Members of the FC receptor homolog gene family (FCRH1-3, 6), related reagents, and uses thereof

ABSTRACT

The invention relates to members of the Fc receptor homolog (FcRH) subfamily, as well as fragments and variants thereof. Each FcRH is a Type I transmembrane receptor, preferably, comprises an extracellular region, a transmembrane region, and a cytoplasmic region. The cytoplasmic region preferably comprises one or more immunoreceptor tyrosine-based inhibitory or activation motifs (“ITIMs” or “ITAMs). The invention provides polypeptides, nucleic acids, vectors, expression systems, and antibodies and antibody fragments related to the FcRHs as well as uses thereof. Such uses include uses in the diagnosis and treatment of a malignancy of hematopoietic cell lineage or an inflammatory or autoimmune disease in a subject and in the modulation of a humoral immune response in a subject.

This application claims the benefit of U.S. Provisional Application No. 60/367,667, filed Mar. 25, 2002.

ACKNOWLEDGEMENTS

This invention was made with government support under Grants 2R37 and AI39816 awarded by NIAID. The government has certain rights in the invention.

FIELD OF THE INVENTION

This invention relates generally to immunology and modulation of immunologic responses in the context of inflammatory diseases and cancer.

BACKGROUND OF THE INVENTION

Receptors for the Fc region (FcRs) of Igs have broad tissue distribution patterns and can modulate cellular and humoral immunity by linking their antibody ligands with effector cells of the immune system (Ravetch, J. V. & Kinet, J.-P. (1991) Annu. Rev. Immunol. 9, 457-492; Daeron, M. (1997) Annu. Rev. Immunol. 15, 203-234. These cellular receptors have the ability to sense humoral concentrations of antibody, initiate cellular responses in host defense, and participate in autoimmune disorders (Ravetch, J. V. & Bolland, S. (2001) Annu. Rev. Immunol. 19, 275-290). Their diverse regulatory roles depend on the Ig isotype specificity and cellular distribution of the individual FcR. These Ig superfamily members share similarities in their ligand binding subunits, and they may have inhibitory or activating signaling motifs in their intracellular domains or instead pair with signal transducing subunits possessing activating signaling motifs.

Recently, characterization of FcR homologs in mice, the paired Ig-like receptors (Kubagawa, H. et al. (1997) Proc. Natl. Acad. Sci. USA 94, 5261-5266; Hayami, K. et al. (1997) J. Biol. Chem. 272, 7320-7327), and their relatives in humans the Ig-like transcripts/leucocyte Ig-like receptors (Borges, L. et al. (1997) J. Immunol. 159, 5192-5196; Samaridis, J. & Colonna, M. (1997) Eur. J. Immunol. 27, 660-665) have been elucidated. This multigene family, which includes the FcαR (Kremer, E. J. et al. (1992) Hum. Genet. 89, 107-108) and the natural killer cell Ig-like receptors (Wagtmann, N. et al. (1997) Curr. Biol. 7, 615-618), is located in a human chromosome 19q13 region known as the leucocyte receptor complex (LRC) (Wende, H. et al. (1999) Mamm. Genome 10, 154-160; Wilson, M. J. et al. (2000) Proc. Natl. Acad. Sci. USA 97, 4778-4783). These Ig-like multigene families belong to a larger class of receptors characterized by their possession of common cytoplasmic tyrosine-based signaling motifs. These can be either immunoreceptor tyrosine-based activation motifs (ITAMs) containing two repeats of the consensus sequence Y-X-X-L/I spaced by 6-8 amino acids (E/D)-X-X-Y-X-X-(L/I)-X₆₋₈-Y-X-X-(L/I) (SEQ ID NO:64, with six amino acid between the consensus sequences; SEQ ID NO:65, with seven amino acid residues between the consensus sequences; and SEQ ID NO:66, with eight amino acid residues between the consensus sequences) or immunoreceptor tyrosine-based inhibitory motifs (ITIMs) with a 6-amino acid consensus sequence (I/V/L/S)-X-Y-X-X-(L/V) (SEQ ID NO:67) (Reth, M. (1992) Annu. Rev. Immunol. 10, 97-121; Vely, F. & Vivier, E. (1997) J. Immunol. 159, 2075-2077; Ravetch, J. V. & Lanier, L. L. (2000) Science 290, 84-89; Gergely, J. et al. (1999) Immunol. Lett. 68, 3-15). The phylogenetic conservation of these types of receptors in birds (Dennis, G. et al. (2000) Proc. Natl. Acad. Sci. USA 97, 13245-13250) and bony fish (Yoder, J. A. et al. (2001) Proc. Natl. Acad. Sci. USA 98, 6771-6717) is indicative of their biological value. After ligand binding of the activating receptor complexes, ITAM tyrosines are rapidly phosphorylated by Src family kinases to initiate a cascade of signaling events that trigger cellular activation. In the case of ITIM-bearing receptors, the tyrosines provide a docking site for phosphatases containing Src homology 2 domains that can abrogate cellular activation (Long, E. O. (1999) Annu. Rev. Immunol. 17, 875-904; Unkeless, J. C. & Jin, J. (1997) Curr. Opin. Immunol. 9, 338-343). The balance in the utilization of these activating and inhibitory receptor pairs can serve to modulate cellular responses to a variety of stimuli.

The genes encoding the classical FcγRs, FcγRI, FcγRII, FcγRIII, and FcεRI, lie on the long arm of chromosome 1 (1q21-23) near the polymeric Ig receptor (pIgR) and Fcα/μR genes (1q32) (20-23). Members of this FcR subfamily have relatively low extracellular homology with the FcR-related genes that reside in the LRC on chromosome 19. Like the FcγR- and FcεR-activating receptors, the ligand binding chain of the FcαR coassociates with the ITAM containing FcR common γ-chain (Pfefferkorn, L. C. & Yeaman, G. P (1994) J. Immunol. 153, 3228-3236; Morton, E. C. et al. (1995) J. Biol. Chem. 270, 29781-29787). New members of the FcR family were sought which could have diverse signally properties and oncogenic potential.

SUMMARY OF THE INVENTION

In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to members of a cluster of FcR and FcR gene relatives encoded, for example, by genes in the human chromosome 1q21-23 region, or analogous region in non-human subjects. The members are Type I transmembrane receptors, or alternatively spliced forms thereof, with homology to the FcR family and are referred to herein as FcRHs. Each FcRH can comprise an extracellular region, a transmembrane region, and a cytoplasmic region. The cytoplasmic region preferably comprises one or more immunoreceptor tyrosine-based inhibitory or activation motifs (“ITIMs” or “ITAMs).

The invention relates to polypeptides corresponding to isolated FcRHs (e.g., huFcRH 1, 2, 3, and 6 and moFcRH1, 2, and 3), as well as fragments and isoforms thereof. The invention further relates to nucleic acids that encode the FcRHs, as well as hybridization probes related thereto and complementary sequences. The invention further provides vectors and cells related to the nucleic acids of the invention.

The invention further relates to making an FcRH, or a fragment or variant thereof, comprising culturing a cell comprising a vector of the invention under conditions permitting expression of the FcRH. The invention also provides an antibody reagent kit comprising the antibody, or a fragment or variant thereof, and reagents for detecting binding of the antibody, fragment, or antibody variant to a ligand.

The invention further relates to uses of the polypeptides, nucleic acids and antibodies of the invention. For example, the invention relates to methods of diagnosing and methods of treating a malignancy of hematopoietic cell lineage or an inflammatory or autoimmune disease in a subject. The invention also relates to modulation of a humoral immune response in a subject.

Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate (one) several embodiment(s) of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 shows the relative position of the FcRH locus within the FcR cluster on chromosome 1. The cytogenetic location of the FcR genes is approximated from the GenBank Mapview database. The BAC clones (4, GenBank accession no. AL139409; 3, GenBank accession no. AL356276; 2, GenBank accession no. AL135929; and 1, GenBank accession no. AL353721) that span the locus are oriented in relation to their respective FcRH genes (shaded area).

FIG. 2 shows the structural and sequence diversity of FcRH1, FcRH2, and FcRH3. FIG. 2A is a schematic representation of FcRH molecules. The three cDNAs encode type I transmembrane proteins with similar extracellular domains, but different cytoplasmic regions. The extracellular (EC) regions contain different numbers of C2-like Ig domains and potential sites of N-linked glycosylation. The transmembrane (TM) domains are uncharged, except in the case of FcRH1. The cytoplasmic (CY) region of FcRH1 contains two ITAMs (light gray boxes) and one ITAM-like region (small, lined box), whereas FcRH2 contains one ITAM and two ITIMs (dark gray boxes). FcRH3 has a long cytoplasmic tail with one ITAM, one ITIM, and an ITAM-like region. The amino acid length of each region is indicated. FIG. 2B shows the multiple alignment comparison of FcRH1, FcRH2, and FcRH3 amino acid sequences (one-letter code) based on the FcRH3 sequence. Amino acid identity is represented by dots, and gaps are indicated by dashes. Predicted N-linked glycosylation sites and transmembrane domains are underlined in black. Consensus ITAM (bold) and ITIM (bold, underlined) motifs are indicated. Putative structural domains are labeled: SP, signal peptide; EC, extracellular domain; MP-TM, membrane proximal-transmembrane; and CY, cytoplasmic regions. Amino acid lengths are indicated in parentheses.

FIG. 3 shows a composite analysis of the extracellular homology among FcRH and FcR family members. Pairwise analysis of individual Ig-like subunits was performed with the CLUSTAL method algorithm using FcRH3 as the index of comparison. Individual homologous domains are coded to indicate relatedness. Percent amino acid identities for related domains are indicated and aligned in relation to the comparative FcRH3 subunit. The amino acid identity for the membrane proximal domains (light gray subunits) of FcRH5 are provided as the range of identity for all individually related domains. Comparisons that are not applicable are left blank Amino acid sequences were derived from IRTA1 (GenBank accession no. AF343659), IRTA2 (GenBank accession no. AF34364), moFcRH (GenBank accession no. AAG28775) FcγRI (GenBank accession no. AAA35678), FcγRII (Swiss-Prot accession no. P31994), FcγRIII (Swiss-Prot accession no. P08637), FcεRI (Swiss-Prot accession no. P12319), and FcαRI (Swiss-Prot accession no. P24071).

FIG. 4 shows the relative location of the mouse FcR family. Location is indicated in reference to the human FcR related genes at Ch 1q21-23 and their orthologous loci on mouse Ch 3 and Ch 1. The microsatellite marker d3Mit187 is located within moFcRH1.

FIG. 5 shows the multiple alignment comparisons of huFcRH1-5 and mouse FcRH1 and 2 amino acid sequences (one-letter code) based on the FcRH3 sequence. Amino acid gaps are indicated by dashes. Consensus ITAM (underlined) and ITIM (italic, underlined) motifs are indicated. Amino acid lengths are indicated in parentheses.

FIG. 6 shows domains marked to indicate relatedness of the Ig-like subunits. Ig-like domain homology was determined by generation of a phylogenetic tree using DNAStar software with the CLUSTAL program and assigning arbitrary colors to individual Ig-domains of a given branch. Amino acid identities for full length, extracellular and, cytoplasmic domain comparisons are based on huFcRH3. Closest cytoplasmic relatives are indicated in parentheses. Most identical extracellular comparisons between mouse and human relatives are highlighted in horizontal lines. Comparisons that are not applicable are left blank.

FIG. 7 shows the domains of huFcRH1-6, moFcRH1-3 and related proteins. Domains are colored to indicate relatedness of the Ig-like subunits. Ig-like domain homology was determined by generation of a phylogenetic tree using DNAStar software with the CLUSTAL program and assigning arbitrary colors to individual Ig-domains of a given branch. Amino acid identities for fill length, extracellular and, cytoplasmic domain comparisons are based on huFcRH3. Closest cytoplasmic relatives are indicated in parentheses. Most identical extracellular comparisons between mouse and human relatives are highlighted in red. Comparisons that are not applicable are left blank.

FIG. 8 shows the structural characteristics of the mouse FcRH isoforms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the Examples included therein and to the Figures and their previous and following description.

In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings:

As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a receptor includes mixtures of various receptors, reference to “a pharmaceutical carrier” includes mixtures of two or more such carriers, and the like.

Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, the phrase “optionally contains two ITAM consensus motifs” means that the two ITAMs may or may not be present and that the description includes both the presence and absence of two ITAM consensus motifs.

As used throughout, by “subject” is meant an individual. Preferably, the subject is a mammal such as a primate, and, more preferably, a human. The term “subject” can include domesticated animals, such as cats, dogs, etc., livestock (e.g., cattle, horses, pigs, sheep, goats, etc.), and laboratory animals (e.g., mouse, rabbit, rat, guinea pig, etc.).

By “isolated nucleic acid” is meant a nucleic acid the structure of which is not identical to that of the naturally occurring nucleic acid or to that of any fragment of the naturally occurring genomic nucleic acid spanning more than three separate genes. The term therefore covers, for example, (a) a DNA which has the sequence of part of the naturally occurring genomic DNA molecules but is not flanked by both of the coding sequences that flank that part of the molecule in the genome of the organism in which it naturally occurs; (b) a nucleic acid incorporated into a vector or into the genomic DNA of a prokaryote or eukaryote in a maimer such that the resulting molecule is not identical to any naturally occurring vector or genomic DNA; (c) a separate molecule such as cDNA, a genomic fragment, a fragment produced by polymerase chain reaction, or a restriction fragment; and (d) a recombinant nucleotide sequence that is part of a hybrid gene, i.e., a gene encoding a fusion protein.

By “label” is meant any detectable tag that can be attached directly (e.g. a fluorescent molecule integrated into a polypeptide or nucleic acid) or indirectly (e.g., by way of binging to a primary antibody a secondary antibody with an integrated fluorscent molecule) to the molecule of interest. A “label” is any tag that can be visualized with imaging methods. The detectable tag can be a radio-opaque substance, radiolabel a fluorescent label, or a magnetic label. The detectable tag can be selected from the group consisting of gamma-emitters, beta-emitters, and alpha emitters, gamma-emitters, positron-emitters, X-ray-emitters and fluorescence-emitters suitable for localization. Suitablle fluorescent compounds include fluorescein sodium, fluorescein isothiocyanate, phycoerythrin, and TEXAS RED® sulfonyl chiloride (Molecular Probes, Eugene, OR). See, de Belder & Wik (Preparation and properties of fluorescein-labelled hyaluronate. Carbohydr. Res.44(2):251-57 (1975). Those skilled in the art will know, or will be able to ascertain with no more than routine experimentation, other fluorescent compounds that are suitable for labeling the molecule.

Polypeptides

The invention provides members of a cluster of FcR and FcR gene relatives encoded by genes in the human chromosome 1 q21-23 region, or analogous region in non-human subjects, including for example, chromosome 3 in mouse. A consensus amino acid motif, based on the FcγRI, FcγRII, FcγRIII and pIgR extracellular regions, was used in a GenBank protein database query to identify member of the gene subfamily. Genomic clones were identified that were found to contain FcR relatives and are termed the Fc receptor homolog (FcRH) subfamily: specifically, FcRH1, FcRH2, FcRH3, and FcRH6. Also, found were mouse Fc receptor homologs designated moFcR1, 2, and 3.

By “homologous” is meant about 25% percent homology or greater. Homology is also characterized by proximity in the location of the genes and by similarities as identified in a composite analysis. As used herein, “percent homology” of two amino acid sequences or of two nucleic acid sequences is determined using the algorithm of Karlin and Altschul (Proc. Natl. Acad. Sci. USA 87:2264-2268 (1990)). Such an algorithm is incorporated into the NBLAST and XBLAST programs of Altschul et al. (J. Mol. Biol. 215:403-410 (1990)). BLAST nucleotide searches are performed with the NBLAST program, score 100, wordlength=12, to obtain nucleotide sequences homologous to a nucleic acid molecule of the invention. BLAST protein searches are performed with the XBLAST program, score=50, wordlength=3, to obtain amino acid sequences homologous to a reference polypeptide. To obtain gapped alignments for comparison purposes, Gapped Blast is utilized as described in Altschul et al. (Nucl. Acids Res. 25: 3389-3402 (1997)). When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) are used. See http://ww.ncbi.nlm.nih.gov.

By “FcRH” is meant a Type I transmembrane receptor, or an alternatively spliced form thereof, including, for example, a secreted form or a GPI-anchored form, with homology to the classical Fc receptor family. In a preferred embodiment, the FcRH shows homology with the extracellular regions of FcγRI, FcγRII, FcγRIII, or pIgR. More specifically, the FcRH shows homology with an amino acid sequence corresponding with the amino terminal sequences of the second Ig domains of the FcγRs and the third Ig domain of pIgR or FcγRH1. The FcRH can comprise an extracellular region, a transmembrane region, and a cytoplasmic region. The extracellular region preferably comprises one or more Ig domains, and more preferably less than 9, and even more preferably less than 7 or less than 8 Ig domains. Preferably, the cytoplasmic region comprises more than 107 (including more than 108, 109, 110, 111, 112, 113, 114, 115, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, or 145 amino acids). Alternatively, the cytoplasmic region comprises less than 104 amino acids (including less than 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80). The cytoplasmic region preferably comprises one or more immunoreceptor tyrosine-based inhibitory or activation motifs (“ITIMs” or “ITAMs).

The invention provides isolated FcRHs (e.g., huFcRH 1, 2, 3, and 6, and moFcRH1-3, as described in detail below), as well as fragments and isoforms thereof. The isolated amino acid sequences provided herein optionally are combined with a human signal sequence (e.g., MLPRLLLLICAPLCEP (SEQ ID NO:29), MLLWSLLVIFDAVTEQADS (SEQ ID NO:30), MLLWLLLLILTPGREQS (SEQ ID NO:31), MLLWTAVLLFVPCVG (SEQ ID NO:32)) or a mouse signal sequence (e.g., MPLCLLLLVFAPVGVQS (SEQ ID NO:69), MLPWLLLLICALPCEPA (SEQ ID NO:72), MSGSFSPCVVFTQMWLTLLVVTPVN (SEQ ID NO:79)).

In one embodiment, the invention provides huFcRH1 and its fragments and isoforms. Thus, in one embodiment of the isolated FcRH, the extracellular region comprises less than four Ig domains. Preferably, the cytoplasmic region comprises less than 104 amino acids and, even more preferably, comprises less than 104 and more than 86 amino acids. In one embodiment, the transmembrane region comprises an acidic amino acid (e.g., glutamate or aspartate). The isolated FcRH of the invention comprises a cytoplasmic region having the amino acid sequence of SEQ ID NO:1, in the presence or absence of conservative amino acid substitutions. Further provided is the isolated FcRH, wherein the extracellular region comprises the amino acid sequence of SEQ ID NO:21, in the presence or absence of conservative amino acid substitutions, and in the presence and absence of a signal sequence. More specifically, the isolated FcRH comprises the amino acid sequence of SEQ ID NO:2, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. In one embodiment the signal sequence is MLPRLLLLICAPLCEP (SEQ ID NO:29). In a preferred embodiment, the FcRH of the invention is expressed by myeloid cells (e.g., granulocytes and monocytes). Additional characteristics of the full length FcRH1 include a predicted molecular weight of about 46-47 kDaltons; about 425-435 (e.g., 429) amino acids in length with about 35 strongly basic(+) amino acids (K,R), about 45 strongly acidic(−) amino acids (D,E), about 144 hydrophobic amino acids (A,I,L,F,W,V), and about 127 polar amino acids (N,C,Q,S,T,Y); a predicted isolelectric point of about 5-5.5 (e.g., 5.310); and charge of about −9 at PH 7.0.

In another embodiment, the invention provides an isolated FcRH corresponding to huFcRH2, its fragments, or isoforms. Thus, the invention provides a FcRH wherein the cytoplasmic region comprises less than 99 amino acids (e.g., 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98) and wherein the receptor further comprises an extracellular domain with up to four Ig domains and up to five N-linked glycosylation sites. More specifically, the isolated FcRH has a cytoplasmic region that comprises the amino acid sequence of SEQ ID NO:3, in the presence or absence of conservative amino acid substitutions, or an extracellular region comprising SEQ ID NO:22, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. Even more specifically, the isolated FcRH comprises the amino acid sequence of SEQ ID NO:4, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. In one embodiment, the signal sequence WSLLVIFDAVTEQADS (SEQ ID NO:30). Additional characteristics of the fall length FcRH1 include a predicted molecular weight of about 50-60 kDaltons; about 495-515 (e.g., 508) amino acids in length with about 44 strongly basic(+) amino acids (K,R), about 49 strongly acidic(−) amino acids (D,E), about 175 hydrophobic amino acids (A,I,L,F,W,V), and about 161 polar amino acids (N,C,Q,S,T,Y); a predicted isolelectric point of about 6-6.5 (e.g., 6.188); and charge of about −4 at PH 7.0.

In another embodiment, the invention provides huFcRH3, its fragments, and isoforms. More specifically, the invention provides an isolated FcRH having a cytoplasmic region that comprises more than 107 amino acids (e.g., 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 212, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 247, 148, 149, 150 amino acids). Optionally, the isolated FcRH has a cytoplasmic region comprising one ITAM and one ITIM. More specifically, the cytoplasmic region comprises the amino acid sequence of SEQ ID NO:5 or SEQ ID NO:23, in the presence or absence of conservative amino acid substitutions. In one embodiment, the extracellular domain of the FcRH comprises the amino acid sequence of SEQ ID NO:24, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. Also provided is an isolated FcRH comprising the amino acid sequence of SEQ ID NO:6 or SEQ ID NO:25, in the presence or absence of one or more amino acid substitutions, and in the presence or absence of a signal sequence. In one embodiment the signal sequence comprises MLLWLLLLILTPGREQS (SEQ ID NO:31). Additional characteristics of the full length FcRH1 include a predicted molecular weight of about 80-90 kDaltons; about 725-740 (e.g., 734) amino acids in length with about 68 strongly basic(+) amino acids (K,R), about 75 strongly acidic(−) amino acids (D,E), about 232 hydrophobic amino acids (A,I,L,F,W,V), and about 224 polar amino acids (N,C,Q,S,T,Y); a predicted isolelectric point of about 6.5-7.0 (e.g., 6.852); and charge of about −2 at PH 7.0.

The invention further provides an isolated huFcRH6, its fragments, and isoforms. More specifically, the FcRH comprises a cytoplasmic region having the amino acid sequence of SEQ ID NO:26, in the presence or absence or one or more conservative amino acid substitutions. The extracellular domain comprises the amino acid sequence of SEQ ID NO:27, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. Also, provided by the invention is a FcRH having the amino acid substitutions of SEQ ID NO:28, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. In one embodiment the signal sequence is MLLWTAVLLFVPCVG (SEQ ID NO:32).

The invention further provides a polypeptide comprising the amino acid sequence of SEQ ID NO:1, 21, 2, 3, 22, 4, 5, 23, 24, 6, 25, 26, 27, or 28, in the presence or absence of conservative amino acid substitutions. The invention also provides a polypeptide having at least 80, 85, 90, or 95% homology with SEQ ID NOs: 1, 21, 2, 3, 22, 4, 5, 23, 24, 6, 25, 26, 27, or 28.

The invention further provides an isolated moFcRH1 isoform, its fragments, and isoforms. The moFcRH1 is an isoform of SEQ ID NO:68. More specifically, the FcRH comprises four Ig domains, optionally having the sequence of SEQ ID NO: 70, in the presence or absence or one or more conservative amino acid substitutions, and in the presence or absence of a signal sequence (e.g., the sequence of SEQ ID NO:71).

The invention further provides an isolated moFcRH2, its fragments, and isoforms. The provided isoforms include one isoform with a transmembrane region and one isoform lacking the transmembrane region. More specifically, the FcRH comprises a cytoplasmic region having the amino acid sequence of SEQ ID NO:76, in the presence or absence or one or more conservative amino acid substitutions. The extracellular domain comprises the amino acid sequence of SEQ ID NO:74, in the presence or absence of conservative amino acid substitutions, and in the presence or absence of a signal sequence. Also, provided by the invention is a FcRH having the amino acid sequence of SEQ ID NO:73, which comprises a transmembrane region, or SEQ ID NO:77, which lacks the transmembrane region. In each case, the FcRH sequence can include the presence or absence of conservative amino acid substitutions, and the presence or absence of a signal sequence. In one embodiment the signal sequence is the sequence of SEQ ID NO:72.

The invention also provided a moFcRH3, its fragments and isoforms. The cytoplasmic region can comprise the amino acid sequence of SEQ ID NO:81, in the presence or absence of conservative amino acid substitutions. Optionally, the extracellular domain comprises the amino acid sequence of SEQ ID NO:80, in the presence or absence of conservative amino acid substitutions or in the presence or absence of a signal sequence (e.g., the sequence of SEQ ID NO:79). The full length sequence optionally has the amin oacid sequence of SEQ ID NO:78, in the presence or absence of conservative amino acid substitutions or in the presence or absence of a signal sequence (e.g., the sequence of SEQ ID NO:79).

Fragments, variants, or isoforms of the FcRHs of the invention are provided. It is understood that these terms include functional variants. Fragments can include the cytoplasmic region, the extracellular region, the transmembrane region or any portion of at least 10 amino acids or any combination of the regions or portions. The variants are produced by making amino acid substitutions, deletions, and insertions, as well as post-translational modifications. Variations in post-translational modifications can include variations in the type or amount of carbohydrate moieties of the protein core or any fragment or derivative thereof. Variations in amino acid sequence may arise naturally as allelic variations (e.g., due to genetic polymorphism) or may be produced by human intervention (e.g., by mutagenesis of cloned DNA sequences), such as induced point, deletion, insertion and substitution mutants. These modifications can result in changes in the amino acid sequence, provide silent mutations, modify a restriction site, or provide other specific mutations.

Amino acid sequence modifications fall into one or more of three classes: substitutional, insertional or deletional variants. Insertions include amino and/or carboxyl terminal fusions as well as intrasequence insertions of single or multiple amino acid residues. Insertions ordinarily will be smaller insertions than those of amino or carboxyl terminal fusions, for example, on the order of one to four residues. Deletions are characterized by the removal of one or more amino acid residues from the protein sequence. Typically, no more than about 2 to 6 residues are deleted at any one site within the protein molecule. These variants ordinarily are prepared by site-specific mutagenesis of nucleotides in the DNA encoding the protein, thereby producing DNA encoding the variant, and thereafter expressing the DNA in recombinant cell culture. Techniques for making substitution mutations at predetermined sites in DNA having a known sequence are well known and include, for example, M13 primer mutagenesis and PCR mutagenesis. Amino acid substitutions are typically of single residues but may include multiple substitutions at different positions; insertions usually will be on the order of about from 1 to 10 amino acid residues but can be more; and deletions will range about from 1 to 30 residues, but can be more. Deletions or insertions preferably are made in adjacent pairs, i.e. a deletion of 2 residues or insertion of 2 residues. Substitutions, deletions, insertions or any combination thereof may be combined to arrive at a final construct. The mutations must not place the sequence out of reading frame and preferably will not create complementary regions that could produce secondary mRNA structure. Substitutional variants are those in which at least one residue has been removed and a different residue inserted in its place. Such substitutions generally are made in accordance with Table 1 and are referred to as conservative substitutions.

TABLE 1 Amino Acid Substitutions Original Residue Exemplary Substitutions Ala Ser Arg Lys Asn Gln Asp Glu Cys Ser Gln Asn Glu Asp Gly Pro His Gln Ile Leu; Val Leu Ile; Val Lys Arg; Gln Met Leu; Ile Phe Met; Leu; Tyr Ser Thr Thr Ser Trp Tyr Tyr Trp; Phe Val Ile; Leu

Substantial changes in function or immunological identity are made by selecting substitutions that are less conservative than those in Table 1, i.e., selecting residues that differ more significantly in their effect on maintaining (a) the structure of the polypeptide backbone in the area of the substitution, for example as a sheet or helical conformation, (b) the charge or hydrophobicity of the molecule at the target site or (c) the bulk of the side chain. The substitutions that in general are expected to produce the greatest changes in the protein properties will be those in which (a) a hydrophilic residue, e.g. seryl or threonyl, is substituted for (or by) a hydrophobic residue, e.g. leucyl, isoleucyl, phenylalanyl, valyl or alanyl; (b) a cysteine or proline is substituted for (or by) any other residue; (c) a residue having an electropositive side chain, e.g., lysyl, arginyl, or histidyl, is substituted for (or by) an electronegative residue, e.g., glutamyl or aspartyl; or (d) a residue having a bulky side chain, e.g., phenylalanine, is substituted for (or by) one not having a side chain, e.g., glycine, in this case, (e) by increasing the number of sites for sulfation and/or glycosylation.

Substitutional or deletional mutagenesis can be employed to insert sites for N-glycosylation (Asn-X-Thr/Ser) or O-glycosylation (Ser or Thr). Deletions of cysteine or other labile residues also may be desirable. Deletions or substitutions of potential proteolysis sites, e.g. Arg, is accomplished for example by deleting one of the basic residues or substituting one by glutaminyl or histidyl residues.

Certain post-translational derivatizations are the result of the action of recombinant host cells on the expressed polypeptide. Glutaminyl and asparaginyl residues are frequently post-translationally deamidated to the corresponding glutamyl and asparyl residues. Alternatively, these residues are deamidated under mildly acidic conditions. Other post-translational modifications include hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of the o-amino groups of lysine, arginine, and histidine side chains (T. E. Creighton, Proteins: Structure and Molecular Properties, W. H. Freeman & Co., San Francisco pp 79-86 [1983]), acetylation of the N-terminal amine and, in some instances, amidation of the C-terminal carboxyl. Modifications in the FcRH can also include modifications in glycosylation.

In all mutational events, it is understood that the controlling aspect of the mutation is the function that the subsequent protein possesses. The preferred mutations are those that do not detectably change the desired function or that increase the desired function.

Nucleic Acids

Also provided is an isolated nucleic acid that encodes the FcRH of the invention. The nucleic acid can be single or double stranded and can be RNA or DNA. More specifically, the invention provides an isolated nucleic acid, comprising a nucleotide sequence that encodes SEQ ID NO:1, SEQ ID NO:21, SEQ ID NO:2. SEQ ID NO: 3, SEQ ID NO:22, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, or SEQ ID NO:6, SEQ ID NO:70, SEQ ID NO:73, SEQ ID NO:74, SEQ ID NO:76, SEQ ID NO:77, SEQ ID NO:78, SEQ ID NO:80, SEQ ID NO:81, optionally with conservative amino acid substitutions. Optionally the nucleic acid further encodes a signal sequence (e.g., the signal sequences of SEQ ID NO:29, 30, 31, 32, 71, 75, 79). The isolated nucleic acid optionally encodes the sequences with 80, 85, 90, or 95% identity. More specifically, the invention provides an isolated nucleic acid, comprising a nucleotide sequence of SEQ ID NO:7, SEQ ID NO:13, SEQ ID NO:8, SEQ ID NO:34, SEQ ID NO:9, SEQ ID NO:14, SEQ ID NO:10, SEQ ID NO:36, SEQ ID NO:11, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:12, SEQ ID NO:38, SEQ ID NO:17, SEQ ID NO:18, SEQ ID NO:19, SEQ ID NO:20; SEQ ID NO:40, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, SEQ ID NO:92, SEQ ID NO:93, SEQ ID NO:94, SEQ ID NO:95, SEQ ID NO:96, SEQ ID NO:97, SEQ ID NO:98, SEQ ID NO:99, SEQ ID NO:100, SEQ ID NO:101, or SEQ ID NO:102. Optionally, the isolated nucleic acid can further included bases that encode a signal sequence and thus the nucleotide sequence encoding the extracellular region or full-length huFcRH1, 2, 3, or 6 can optionally further comprise the nucleotide sequence of SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39. Optionally, the isolated nucleic acids for moFcRHs include nucleic acid sequences that encode signal sequences as well, including for example, those portions of nucleic acid sequences SEQ ID NO:101, SEQ ID NO:97, SEQ ID NO:94, SEQ ID NO:91, SEQ ID NO:88, SEQ ID NO:84.

Preferably the nucleic acid that encodes the full length FcRH1 includes about 290 bases. The nucleic acid that encodes the full length FcRH2 includes about 1527 bases, and the nucleic acid that encodes the full length FcRH3 includes about 2205 bases.

The invention also provides an isolated nucleic acid comprising a sequence that hybridizes under stringent conditions to a hybridization probe, wherein the hybridization probe comprises the nucleotide sequence of SEQ ID NO:7, SEQ ID NO:13, SEQ ID NO:8, SEQ ID NO:34, SEQ ID NO:9, SEQ ID NO:14, SEQ ED NO:10, SEQ ID NO:36, SEQ ID NO:11, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:12, SEQ ID NO:38, SEQ ID NO:17, SEQ ID NO:18, SEQ ID NO:19, and SEQ ID NO:20; SEQ ID NO:40, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, SEQ ID NO:92, SEQ ID NO:93, SEQ ID NO:94, SEQ ID NO:95, SEQ ID NO:96, SEQ ID NO:97, SEQ ID NO:98, SEQ ID NO:99, SEQ ID NO:100, SEQ ID NO:101, or SEQ ID NO:102, or the complement of either sequence.

Further provided is a single stranded nucleic acid that hybridizes under stringent conditions to a nucleic acid having the sequence of SEQ ID NO:7, SEQ ID NO:13, SEQ ID NO:8, SEQ ID NO:34, SEQ ID NO:9, SEQ ID NO:14, SEQ ID NO:10, SEQ ID NO:36, SEQ ED NO:11, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:12, SEQ ID NO:38, SEQ ID NO:17, SEQ ID NO:18, SEQ ID NO:19, and SEQ ID NO:20; SEQ ID NO:40, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, SEQ ID NO:92, SEQ ID NO:93, SEQ ID NO:94, SEQ ID NO:95, SEQ ID NO:96, SEQ ID NO:97, SEQ ID NO:98, SEQ ID NO:99, SEQ ID NO:100, SEQ ID NO:101, or SEQ ID NO:102.

By “hybridizing under stringent conditions” or “hybridizing under highly stringent conditions” is meant that the hybridizing portion of the hybridizing nucleic acid, typically comprising at least 15 (e.g., 20, 25, 30, or 50 nucleotides), hybridizes to all or a portion of the provided nucleotide sequence under stringent conditions. The term “hybridization” typically means a sequence driven interaction between at least two nucleic acid molecules, such as a primer or a probe and a gene. Sequence driven interaction means an interaction that occurs between two nucleotides or nucleotide analogs or nucleotide derivatives in a nucleotide specific manner. For example, G interacting with C or A interacting with T are sequence driven interactions. Typically sequence driven interactions occur on the Watson-Crick face or Hoogsteen face of the nucleotide. The hybridization of two nucleic acids is affected by a number of conditions and parameters known to those of skill in the art. For example, the salt concentrations, pH, and temperature of the reaction all affect whether two nucleic acid molecules will hybridize. Generally, the hybridizing portion of the hybridizing nucleic acid is at least 80%, for example, at least 90%, 95%, or 98%, identical to the sequence of or a portion of a nucleic acid encoding an FcRH of the invention, or its complement. Hybridizing nucleic acids of the invention can be used, for example, as a cloning probe, a primer (e.g., for PCR), a diagnostic probe, or an antisense probe. Hybridization of the oligonucleotide probe to a nucleic acid sample typically is performed under stringent conditions. Nucleic acid duplex or hybrid stability is expressed as the melting temperature or Tm, which is the temperature at which a probe dissociates from a target DNA. This melting temperature is used to define the required stringency conditions. If sequences are to be identified that are related and substantially identical to the probe, rather than identical, then it is useful to first establish the lowest temperature at which only homologous hybridization occurs with a particular concentration of salt (e.g., SSC or SSPE). Assuming that a 1% mismatch results in a 1° C. decrease in the Tm, the temperature of the final wash in the hybridization reaction is reduced accordingly (for example, if sequence having >95% identity with the probe are sought, the final wash temperature is decreased by 5° C.). In practice, the change in Tm can be between 0.5° C. and 1.5° C. per 1% mismatch. Stringent conditions involve hybridizing at 68° C. in 5×SSC/5× Denhardt's solution/1.0% SDS, and washing in 0.2×SSC/0.1% SDS at room temperature. Moderately stringent conditions include washing in 3×SSC at 42° C. The parameters of salt concentration and temperature can be varied to achieve the optimal level of identity between the probe and the target nucleic acid. Additional guidance regarding such conditions is readily available in the art, for example, in Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Press, NY; and Ausubel et al. (eds.), 1995, Current Protocols in Molecular Biology, (John Wiley & Sons, NY) at Unit 2.10.

The nucleic acids of the present invention are optionally labeled, directly or indirectly. Such labeled nucleic acids are useful in various diagnostic techniques including for example, in situ hybridization, FISH, in situ PCR, and PRINS. Both methods involve the preparation of short sequences of single-stranded nucleic acid probes that are complementary to the nucleic acid sequences that encode an FcRH. See, e.g., M Andreeff and D Pinkel (1999), An Introduction to Flourescent In-Situ Hybridization: Principles and Clinical Applications, John Wiley & Sons, Ltd; Roche Applied Sciences (2000), Nonradioactive In Situ Hybridization Application Manual; Roche Applied Sciences (1999), PCR Manual, 2d edition, which are incorporated in their entirety for methods of using nucleic acids.

Vectors, Cells, and Methods of Using

Also provided is an expression vector comprising a nucleic acid of the invention, wherein the nucleic acid is operably linked to an expression control sequence. A wide variety of expression system/regulatory sequence combinations may be employed in expressing the disclosed. Such useful regulatory sequences include, for example, the early or late promoters of SV40, CMV, vaccinia, polyoma or adenovirus, the lac system, the trp system, the TAC system, the TRC system, the LTR system, the major operator and promoter regions of phage lambda, the control regions of fd coat protein, the promoter for 3-phosphoglycerate kinase or other glycolytic enzymes, the promoters of acid phosphatase (for example, Pho5), the AOX 1 promoter of methylotrophic yeast, the promoters of the yeast a-mating factors, and other sequences known to control the expression of genes of prokaryotic or eukaryotic cells or their viruses, and various combinations thereof.

Such an expression vector can be designed to be expressed by eukaryotic cells or prokaryotic cells. The vectors of the present invention thus provide DNA molecules which are capable of integration into a prokaryotic or eukaryotic chromosome and expression. The inserted genes in viral and retroviral vectors usually contain promoters, and/or enhancers to help control the expression of the desired gene product. A promoter is generally a sequence or sequences of DNA that function when in a relatively fixed location in regard to the transcription start site. A promoter contains core elements required for basic interaction of RNA polymerase and transcription factors, and may contain upstream elements and response elements. It has been shown that all specific regulatory elements can be cloned and used to construct expression vectors that are selectively expressed in specific cell types. For example, the glial fibrillary acetic protein (GFAP) promoter has been used to selectively express genes in cells of glial origin. Expression vectors used in eukaryotic host cells (e.g., yeast, fungi, insect, plant, animal, human or nucleated cells) may also contain sequences necessary for the termination of transcription which may affect mRNA expression. These regions are transcribed as polyadenylated segments in the untranslated portion of the mRNA encoding tissue factor protein. The 3′ untranslated regions also include transcription termination sites. It is preferred that the transcription unit also contain a polyadenylation region. One benefit of this region is that it increases the likelihood that the transcribed unit will be processed and transported like mRNA. The identification and use of polyadenylation signals in expression constructs is well established. It is preferred that homologous polyadenylation signals be used in the transgene constructs. In certain transcription units, the polyadenylation region is derived from the SV40 early polyadenylation signal and consists of about 400 bases. It is also preferred that the transcribed units contain other standard sequences alone or in combination with the above sequences improve expression from, or stability of, the construct.

The invention further provides transfer vectors, which include any nucleotide construction used to deliver genes into cells (e.g., a plasmid), or as part of a general strategy to deliver genes, e.g., as part of recombinant retrovirus or adenovirus (Ram et al. Cancer Res. 53:83-88, (1993)). As used herein, plasmid or viral vectors are agents that transport the disclosed nucleic acids into the cell without degradation and include a promoter yielding expression of the gene in the cells into which it is delivered. In some embodiments the FcRHs are derived from either a virus or a retrovirus. Viral vectors include, for example, Adenovirus, Adeno-associated virus, Herpes virus, Vaccinia virus, Polio virus, AIDS virus, neuronal trophic virus, Sindbis and other RNA viruses, including these viruses with the HIV backbone. Also preferred are any viral families that share the properties of these viruses that make them suitable for use as vectors. Retroviruses include Murine Maloney Leukemia virus, MMLV, and retroviruses that express the desirable properties of MMLV as a vector. Retroviral vectors are able to carry a larger genetic payload, i.e., a transgene or marker gene, than other viral vectors, and for this reason are a commonly used vector. However, they are not as useful in non-proliferating cells. Adenovirus vectors are relatively stable and easy to work with, have high titers, and can be delivered in aerosol formulation, and can transfect non-dividing cells. Pox viral vectors are large and have several sites for inserting genes, they are thermostable and can be stored at room temperature. A preferred embodiment is a viral vector which has been engineered so as to suppress the immune response of the host organism, elicited by the viral antigens.

Viral vectors can have higher transaction (ability to introduce genes) abilities than chemical or physical methods to introduce genes into cells. Typically, viral vectors contain, nonstructural early genes, structural late genes, an RNA polymerase III transcript, inverted terminal repeats necessary for replication and encapsidation, and promoters to control the transcription and replication of the viral genome. When engineered as vectors, viruses typically have one or more of the early genes removed and a gene or gene/promotor cassette is inserted into the viral genome in place of the removed viral DNA. Constructs of this type can carry up to about 8 kb of foreign genetic material. The necessary functions of the removed early genes are typically supplied by cell lines that have been engineered to express the gene products of the early genes in trans.

A retrovirus is an animal virus belonging to the virus family of Retroviridae, including any types, subfamilies, genus, or tropisms. Retroviral vectors, in general, are described by Verma, I. M., Retroviral vectors for gene transfer. In Microbiology-1985, American Society for Microbiology, pp. 229-232, Washington, (1985), which is incorporated by reference herein. Examples of methods for using retroviral vectors for gene therapy are described in U.S. Pat. Nos. 4,868,116 and 4,980,286; PCT applications WO 90/02806 and WO 89/07136; and Mulligan, (Science 260:926-932 (1993)); the teachings of which are incorporated herein by reference. A retrovirus is essentially a package which has packed into it nucleic acid cargo. The nucleic acid cargo carries with it a packaging signal, which ensures that the replicated daughter molecules will be efficiently packaged within the package coat. In addition to the package signal, there are a number of molecules that are needed in cis, for the replication, and packaging of the replicated virus. Typically a retroviral genome, contains the gag, pol, and env genes which are involved in the making of the protein coat. It is the gag, pol, and env genes which are typically replaced by the foreign DNA that it is to be transferred to the target cell. Retrovirus vectors typically contain a packaging signal for incorporation into the package coat, a sequence which signals the start of the gag transcription unit, elements necessary for reverse transcription, including a primer binding site to bind the tRNA primer of reverse transcription, terminal repeat sequences that guide the switch of RNA strands during DNA synthesis, a purine rich sequence 5′ to the 3′ LTR that serve as the priming site for the synthesis of the second strand of DNA synthesis, and specific sequences near the ends of the LTRs that enable the insertion of the DNA state of the retrovirus to insert into the host genome. The removal of the gag, pol, and env genes allows for about 8 kb of foreign sequence to be inserted into the viral genome, become reverse transcribed, and upon replication be packaged into a new retroviral particle. This amount of nucleic acid is sufficient for the delivery of a one to many genes depending on the size of each transcript. It is preferable to include either positive or negative selectable markers along with other genes in the insert.

Since the replication machinery and packaging proteins in most retroviral vectors have been removed (gag, pol, and env), the vectors are typically generated by placing them into a packaging cell line. A packaging cell line is a cell line that has been transfected or transformed with a retrovirus that contains the replication and packaging machinery, but lacks any packaging signal. When the vector carrying the DNA of choice is transfected into these cell lines, the vector containing the gene of interest is replicated and packaged into new retroviral particles, by the machinery provided in cis by the helper cell. The genomes for the machinery are not packaged because they lack the necessary signals.

The construction of replication-defective adenoviruses has been described (Berkner et al., J. Virology 61:1213-1220 (1987); Massie et al., Mol. Cell. Biol. 6:2872-2883 (1986); Haj-Ahmad et al., J. Virology 57:267-274 (1986); Davidson et al., J. Virology 61:1226-1239 (1987); Zhang, Generation and identification of recombinant adenovirus by liposome-mediated transfection and PCR analysis, BioTechniques 15:868-872 (1993)). The benefit of the use of these viruses as vectors is that they are limited in the extent to which they can spread to other cell types, since they can replicate within an initial infected cell, but are unable to form new infectious viral particles. Recombinant adenoviruses have been shown to achieve high efficiency gene transfer after direct, in vivo delivery to airway epithelium, hepatocytes, vascular endothelium, CNS parenchyma and a number of other tissue sites (Morsy, J. Clin. Invest. 92:1580-1586 (1993); Kirshenbaum, J. Clin. Invest. 92:381-387 (1993); Roessler, J. Clin. Invest. 92:1085-1092 (1993); Moullier, Nature Genetics 4:154-159 (1993); La Salle, Science 259:988-990 (1993); Gomez-Foix, J. Biol. Chem. 267:25129-25134 (1992); Rich, Human Gene Therapy 4:461-476 (1993); Zabner, Nature Genetics 6:75-83 (1994); Guzman, Circulation Research 73:1201-1207 (1993); Bout, Human Gene Therapy 5:3-10 (1994); Zabner, Cell 75:207-216 (1993); Caillaud, Eur. J. Neuroscience 5:1287-1291 (1993); and Ragot, J. Gen. Virology 74:501-507 (1993)). Recombinant adenoviruses achieve gene transduction by binding to specific cell surface receptors, after which the virus is internalized by receptor-mediated endocytosis, in the same manner as wild type or replication-defective adenovirus (Chardonnet and Dales, Virology 40:462-477 (1970); Brown and Burlingham, J. Virology 12:386-396 (1973); Svensson and Persson, J. Virology 55:442-449 (1985); Seth, et al., J. Virol. 51:650-655 (1984); Seth, et al., Mol. Cell. Biol. 4:1528-1533 (1984); Varga et al., J. Virology 65:6061-6070 (1991); Wickham et al., Cell 73:309-319 (1993)).

A viral vector can be one based on an adenovirus which has had the E1 gene removed and these virons are generated in a cell line such as the human 293 cell line. In another preferred embodiment both the E1 and E3 genes are removed from the adenovirus genome.

Another type of viral vector is based on an adeno-associated virus (AAV). This defective parvovirus is a preferred vector because it can infect many cell types and is nonpathogenic to humans. AAV type vectors can transport about 4 to 5 kb and wild type AAV is known to stably insert into chromosome 19. Vectors which contain this site specific integration property are preferred. An especially preferred embodiment of this type of vector is the P4.1 C vector produced by Avigen, San Francisco, Calif., which can contain the herpes simplex virus thymidine kinase gene, HSV-tk, and/or a marker gene, such as the gene encoding the green fluorescent protein, GFP.

In another type of AAV virus, the AAV contains a pair of inverted terminal repeats (ITRs) which flank at least one cassette containing a promoter which directs cell-specific expression operably linked to a heterologous gene. Heterologous in this context refers to any nucleotide sequence or gene which is not native to the AAV or B19 parvovirus.

Typically the AAV and B19 coding regions have been deleted, resulting in a safe, noncytotoxic vector. The AAV ITRs, or modifications thereof, confer infectivity and site-specific integration, but not cytotoxicity, and the promoter directs cell-specific expression. U.S. Pat. No. 6,261,834 is herein incorproated by reference for material related to the AAV vector.

Molecular genetic experiments with large human herpesvirusés have provided a means whereby large heterologous DNA fragments can be cloned, propagated and established in cells permissive for infection with herpesviruses (Sun et al., Nature genetics 8: 33-41, 1994; Cotter and Robertson, Curr Opin Mol Ther 5: 633-644, 1999). These large DNA viruses (herpes simplex virus (HSV) and Epstein-Barr virus (EBV), have the potential to deliver fragments of human heterologous DNA >150 kb to specific cells. EBV recombinants can maintain large pieces of DNA in the infected B-cells as episomal DNA. Individual clones carried human genomic inserts up to 330 kb appeared genetically stable The maintenance of these episomes requires a specific EBV nuclear protein, EBNA1, constitutively expressed during infection with EBV. Additionally, these vectors can be used for transfection, where large amounts of protein can be generated transiently in vitro. Herpesvirus amplicon systems are also being used to package pieces of DNA >220 kb and to infect cells that can stably maintain DNA as episomes. Other useful systems include, for example, replicating and host-restricted non-replicating vaccinia virus vectors.

The invention also provides an isolated cell comprising a vector of the invention. The isolated cell can be either a eukaryotic or prokaryotic cell, such as strains of E. coli, Pseudomonas, Bacillus, Streptomyces; fungi such as yeasts (Saccharomyces, and methylotrophic yeast such as Pichia, Candida, Hansenula, and Torulopsis); and animal cells, such as CHO, R1.1, B-W and LM cells, African Green Monkey kidney cells (for example, COS 1, COS 7, BSC1, BSC40, and BMT10), insect cells (for example, Sf9), and human cells and plant cells in tissue culture.

Also provided is a method of making a FcRH, or a fragment or variant thereof comprising culturing a cell comprising a vector of the invention under conditions permitting expression of the FcRH. The method comprises culturing a cell comprising an exogeneous nucleic acid that encodes the FcRH, fragment, or variant, wherein the exogeneous nucleic acid is operably linked to an expression control sequence, and wherein the culture conditions permit expression of the FcRH, fragment, or variant under the control of the expression control sequence; harvesting the medium from the cultured cells, and isolating the FcRH, fragment, or variant from the cell or culture medium. Optionally the exogenous nucleic acid is the nucleotide sequence of SEQ ID NO:7, SEQ ID NO:13, SEQ ID NO:8, SEQ ID NO:34, SEQ ID NO:9, SEQ ID NO:14, SEQ ID NO:10, SEQ D NO:36, SEQ ID NO:11, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:12, SEQ ID NO:38, SEQ ID NO:17, SEQ ID NO:18, SEQ ID NO:19, and SEQ ID NO:20; SEQ ID NO:40, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, SEQ ID NO:92, SEQ ID NO:93, SEQ ID NO:94, SEQ ID NO:95, SEQ ID NO:96, SEQ ID NO:97, SEQ ID NO:98, SEQ ID NO:99, SEQ ID NO:100, SEQ ID NO:101, or SEQ ID NO:102 or a combination thereof. Optionally, the exogenous nucleic acid further comprises a nucleotide sequence that encodes a signal sequence. In the recombinant methods, the cell can be any known host cell, including for example, a prokaryotic or eukaryotic cell. The nucleic acids that are delivered to cells, generally in a plasmid or other vector, typically contain expression controlling systems. For example, the inserted genes in viral and retroviral systems usually contain promoters, and/or enhancers to help control the expression of the desired gene product.

Those skilled in the art of molecular biology will understand that a wide variety of expression systems may be used to produce recombinant FcRH polypeptides (as well as fragments, fusion proteins, and amino acid sequence variants with therapeutic activity) for use in the methods of the invention. Thus, FcRH may be produced using prokaryotic host cells (e.g., Escherichia coli) or eukaryotic host cells (e.g., Saccharomyces cerevisiae, insect cells such as Sf9 cells, or mammalian cells such as CHO cells, COS-1, NIH 3T3, or HeLa cells). These cells are commercially available from, for example, the American Type Culture Collection, Rockville, Md. (see also F. Ausubel et al., Current Protocols in Molecular Biology, John Wiley & Sons, New York, N.Y., 1998). The method of transformation and the choice of expression vector will depend on the host system selected. Transformation and transfection methods are described, e.g., in Ausubel et al., supra, and expression vectors may be chosen from the numerous examples known in the art.

A nucleic acid sequence encoding an FcRH is introduced into a plasmid or other vector, which is then used to transform living cells. Constructs in which a cDNA containing the entire FcRH coding sequence, a fragment of the FcRH coding sequence, amino acid variations of the FcRH coding sequence, or fusion proteins of the aforementioned, inserted in the correct orientation into an expression plasmid, may be used for protein expression. In some cases, for example, it may be desirable to express the FcRH coding sequence under the control of an inducible or tissue-specific promoter.

Eukaryotic expression systems permit appropriate post-translational modifications to expressed proteins. Thus, eukaryotic, and more preferably mammalian expression systems, allow glycosylations patterns comparable to naturally expressed FcRH. Transient transfection of a eukaryotic expression plasmid allows the transient production of FcRH by a transfected host cell. FcRH may also be produced by a stably-transfected mammalian cell line. A number of vectors suitable for stable transfection of mammalian cells are available to the public (e.g., see Pouwels et al., Cloning Vectors: A Laboratory Manual, 1985, Supp. 1987), as are methods for constructing such cell lines (see e.g., F. Ausubel et al., Current Protocols in Molecular Biology, John Wiley & Sons, New York, N.Y., 1998). Another preferred eukaryotic expression system is the baculovirus system using, for example, the vector pBacPAK9, which is available from Clontech (Palo Alto, Calif.). If desired, this system may be used in conjunction with other protein expression techniques, for example, the myc tag approach described by Evan et al. (Mol. Cell Biol. 5:3610-3616, 1985) or analogous tagging approaches, e.g., using a hemagluttinin (HA) tag.

Once the recombinant protein is expressed, it can be isolated from the expressing cells by cell lysis followed by protein purification techniques such as affinity chromatography. In this example, an antibody that specifically binds to FcRH, which may be produced by methods that are well-known in the art, can be attached to a column and used to isolate FcRH. Once isolated, the recombinant protein can, if desired, be purified further, e.g., by high performance liquid chromatography (HPLC; e.g., see Fisher, Laboratory Techniques In Biochemistry And Molecular Biology, Work and Burdon, Eds., Elsevier, 1980).

Antibodies

The invention also provides a purified antibody or immunologic fragment thereof, wherein the antibody or fragment thereof selectively binds to an FcRH. As used herein, the term “antibody” encompasses, but is not limited to, whole immunoglobulin (i.e., an intact antibody) of any class. Native antibodies are usually heterotetrameric glycoproteins, composed of two identical light (L) chains and two identical heavy (H) chains. Typically, each light chain is linked to a heavy chain by one covalent disulfide bond, while the number of disulfide linkages varies between the heavy chains of different immunoglobulin isotypes. Each heavy and light chain also has regularly spaced intrachain disulfide bridges. Each heavy chain has at one end a variable domain (V(H)) followed by a number of constant domains. Each light chain has a variable domain at one end (V(L)) and a constant domain at its other end; the constant domain of the light chain is aligned with the first constant domain of the heavy chain, and the light chain variable domain is aligned with the variable domain of the heavy chain. Particular amino acid residues are believed to form an interface between the light and heavy chain variable domains. The light chains of antibodies from any vertebrate species can be assigned to one of two clearly distinct types, called kappa (k) and lambda (l), based on the amino acid sequences of their constant domains. Depending on the amino acid sequence of the constant domain of their heavy chains, immunoglobulins can be assigned to different classes. There are five major classes of immunoglobulins: IgA, IgD, IgE, IgG and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG-1, IgG-2, IgG-3, and IgG-4; IgA-1 and IgA-2. The heavy chain constant domains that correspond to the different classes of immunoglobulins are called alpha, delta, epsilon, gamma, and mu, respectively.

The term “variable” is used herein to describe certain portions of the variable domains that differ in sequence among antibodies and are used in the binding and specificity of each particular antibody for its particular antigen. However, the variability is not usually evenly distributed through the variable domains of antibodies. It is typically concentrated in three segments called complementarity determining regions (CDRs) or hypervariable regions both in the light chain and the heavy chain variable domains. The more highly conserved portions of the variable domains are called the framework (FR). The variable domains of native heavy and light chains each comprise four FR regions, largely adopting a b-sheet configuration, connected by three CDRs, which form loops connecting, and in some cases forming part of, the b-sheet structure. The CDRs in each chain are held together in close proximity by the FR regions and, with the CDRs from the other chain, contribute to the formation of the antigen binding site of antibodies (see Kabat E. A. et al., “Sequences of Proteins of Immunological Interest” National Institutes of Health, Bethesda, Md. (1987)). The constant domains are not involved directly in binding an antibody to an antigen, but exhibit various effector functions, such as participation of the antibody in antibody-dependent cellular toxicity.

The term “antibody or fragments thereof” can also encompass chimeric antibodies and hybrid antibodies, with dual or multiple antigen or epitope specificities, and fragments, such as F(ab′)₂, Fab′, Fab and the like, including hybrid fragments. Thus, fragments of the antibodies that retain the ability to bind their specific antigens are provided. For example, fragments of antibodies which maintain FcRH binding activity are included within the meaning of the term “antibody or fragment thereof.” Such antibodies and fragments can be made by techniques known in the art and can be screened for specificity and activity according to the methods set forth in the Examples and in general methods for producing antibodies and screening antibodies for specificity and activity (See Harlow and Lane. Antibodies, A Laboratory Manual. Cold Spring Harbor Publications, New York, (1988)).

Also included within the meaning of “antibody or fragments thereof” are conjugates of antibody fragments and antigen binding proteins (single chain antibodies) as described, for example, in U.S. Pat. No. 4,704,692, the contents of which are hereby incorporated by reference.

In one embodiment, the antibody is a monoclonal antibody. The term “monoclonal antibody” as used herein refers to an antibody obtained from a substantially homogeneous population of antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. The monoclonal antibodies herein specifically include “chimeric” antibodies in which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired activity (See, U.S. Pat. No. 4,816,567 and Morrison et al., Proc. Natl. Acad. Sci. USA, 81:6851-6855 (1984)).

Monoclonal antibodies of the invention may be prepared using hybridoma methods, such as those described by Kohler and Milstein, Nature, 256:495 (1975) or Harlow and Lane, Antibodies, A Laboratory Manual. Cold Spring Harbor Publications, New York, (1988). In a hybridoma method, a mouse or other appropriate host animal, is typically immunized with an immunizing agent to elicit lymphocytes that produce or are capable of producing antibodies that will specifically bind to the immunizing agent. Alternatively, the lymphocytes may be immunized in vitro. Preferably, the immunizing agent comprises an FcRH. Traditionally, the generation of monoclonal antibodies has depended on the availability of purified protein or peptides for use as the immunogen. More recently DNA based immunizations have shown promise as a way to elicit strong immune responses and generate monoclonal antibodies. In this approach, DNA-based immunization can be used, wherein DNA encoding a portion of FcRH, preferably the N- or C-terminal region, is injected into the host animal according to methods known in the art.

Generally, either peripheral blood lymphocytes (“PBLs”) are used in methods of producing monoclonal antibodies if cells of human origin are desired, or spleen cells or lymph node cells are used if non-human mammalian sources are desired. The lymphocytes are then fused with an immortalized cell line using a suitable fusing agent, such as polyethylene glycol, to form a hybridoma cell (Goding, “Monoclonal Antibodies: Principles and Practice” Academic Press, (1986) pp. 59-103). Immortalized cell lines are usually transformed mammalian cells, including myeloma cells of rodent, bovine, equine, and human origin. Usually, rat or mouse myeloma cell lines are employed. The hybridoma cells may be cultured in a suitable culture medium that preferably contains one or more substances that inhibit the growth or survival of the unfused, immortalized cells. For example, if the parental cells lack the enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT or HPRT), the culture medium for the hybridomas typically will include hypoxanthine, aminopterin, and thymidine (“HAT medium”), which substances prevent the growth of HGPRT-deficient cells.

Preferred immortalized cell lines are those that fuse efficiently, support stable high level expression of antibody by the selected antibody-producing cells, and are sensitive to a medium such as HAT medium. More preferred immortalized cell lines are murine myeloma lines, which can be obtained, for instance, from the Salk Institute Cell Distribution Center, San Diego, Calif. and the American Type Culture Collection, Rockville, Md. Human myeloma and mouse-human heteromyeloma cell lines also have been described for the production of human monoclonal antibodies (Kozbor, J. Immunol., 133:3001 (1984); Brodeur et al., “Monoclonal Antibody Production Techniques and Applications” Marcel Dekker, Inc., New York, (1987) pp. 51-63).

The culture medium in which the hybridoma cells are cultured can then be assayed for the presence of monoclonal antibodies directed against an FcRH. Preferably, the binding specificity of monoclonal antibodies produced by the hybridoma cells is determined by immunoprecipitation or by an in vitro binding assay, such as radioimmunoassay (RIA) or enzyme-linked immunoabsorbent assay (ELISA). Such techniques and assays are known in the art, and are described further in Harlow and Lane “Antibodies, A Laboratory Manual” Cold Spring Harbor Publications, New York, (1988).

After the desired hybridoma cells are identified, the clones may be subcloned by limiting dilution or FACS sorting procedures and grown by standard methods. Suitable culture media for this purpose include, for example, Dulbecco's Modified Eagle's Medium and RPMI-1640 medium. Alternatively, the hybridoma cells may be grown in vivo as ascites in a mammal.

The monoclonal antibodies secreted by the subclones may be isolated or purified from the culture medium or ascites fluid by conventional immunoglobulin purification procedures such as, for example, protein A-Sepharose, hydroxylapatite chromatography, gel electrophoresis, dialysis, or affinity chromatography.

The monoclonal antibodies may also be made by recombinant DNA methods, such as those described in U.S. Pat No. 4,816,567. DNA encoding the monoclonal antibodies of the invention can be readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of murine antibodies). The hybridoma cells of the invention serve as a preferred source of such DNA. Once isolated, the DNA may be placed into expression vectors, which are then transfected into host cells such as simian COS cells, Chinese hamster ovary (CHO) cells, plasmacytoma cells, or myeloma cells that do not otherwise produce immunoglobulin protein, to obtain the synthesis of monoclonal antibodies in the recombinant host cells. The DNA also may be modified, for example, by substituting the coding sequence for human heavy and light chain constant domains in place of the homologous murine sequences (U.S. Pat. No. 4,816,567) or by covalently joining to the immunoglobulin coding sequence all or part of the coding sequence for a non-immunoglobulin polypeptide. Such a non-immunoglobulin polypeptide can be substituted for the constant domains of an antibody of the invention, or can be substituted for the variable domains of one antigen-combining site of an antibody of the invention to create a chimeric bivalent antibody comprising one antigen-combining site having specificity for FcRH and another antigen-combining site having specificity for a different antigen.

In vitro methods are also suitable for preparing monovalent antibodies. Digestion of antibodies to produce fragments thereof, particularly, Fab fragments, can be accomplished using routine techniques known in the art. For instance, digestion can be performed using papain. Examples of papain digestion are described in WO 10 94/29348 published Dec. 22, 1994, U.S. Pat. No. 4,342,566, and Harlow and Lane, Antibodies, A Laboratory Manual, Cold Spring Harbor Publications, New York, (1988). Papain digestion of antibodies typically produces two identical antigen binding fragments, called Fab fragments, each with a single antigen binding site, and a residual Fc fragment. Pepsin treatment yields a fragment, called the F(ab′)₂ fragment, that has two antigen combining sites and is still capable of cross-linking antigen.

The Fab fragments produced in the antibody digestion also contain the constant domains of the light chain and the first constant domain of the heavy chain. Fab′ fragments differ from Fab fragments by the addition of a few residues at the carboxy terminus of the heavy chain domain including one or more cysteines from the antibody hinge region. The F(ab′)₂ fragment is a bivalent fragment comprising two Fab′ fragments linked by a disulfide bridge at the hinge region. Fab′-SH is the designation herein for Fab′ in which the cysteine residue(s) of the constant domains bear a free thiol group. Antibody fragments originally were produced as pairs of Fab′ fragments which have hinge cysteines between them. Other chemical couplings of antibody fragments are also known.

An isolated immunogenically specific epitope or fragment of the antibody is also provided. A specific immunogenic epitope of the antibody can be isolated from the whole antibody by chemical or mechanical disruption of the molecule. The purified fragments thus obtained can be tested to determine their immunogenicity and specificity by the methods taught herein. Immunoreactive epitopes of the antibody can also be synthesized directly. An immunoreactive fragment is defined as an amino acid sequence of at least about two to five consecutive amino acids derived from the antibody amino acid sequence.

One method of producing proteins comprising the antibodies of the present invention is to link two or more peptides or polypeptides together by protein chemistry techniques. For example, peptides or polypeptides can be chemically synthesized using currently available laboratory equipment using either Fmoc (9-fluorenylmethyl-oxycarbonyl) or Boc (tert -butyloxycarbonoyl) chemistry. (Applied Biosystems, Inc., Foster City, Calif.). One skilled in the art can readily appreciate that a peptide or polypeptide corresponding to the antibody of the present invention, for example, can be synthesized by standard chemical reactions. For example, a peptide or polypeptide can be synthesized and not cleaved from its synthesis resin whereas the other fragment of an antibody can be synthesized and subsequently cleaved from the resin, thereby exposing a terminal group that is functionally blocked on the other fragment. By peptide condensation reactions, these two fragments can be covalently joined via a peptide bond at their carboxyl and amino termini, respectively, to form an antibody, or fragment thereof. (Grant G A (1992) Synthetic Peptides: A User Guide. W. H. Freeman and Co., N.Y. (1992); Bodansky M and Trost B., Ed. (1993) Principles of Peptide Synthesis. Springer-Verlag Inc., NY). Alternatively, the peptide or polypeptide can by independently synthesized in vivo as described above. Once isolated, these independent peptides or polypeptides may be linked to form an antibody or fragment thereof via similar peptide condensation reactions.

For example, enzymatic ligation of cloned or synthetic peptide segments can allow relatively short peptide fragments to be joined to produce larger peptide fragments, polypeptides or whole protein domains (Abrahmsen L et al., Biochemistry, 30:4151 (1991)). Alternatively, native chemical ligation of synthetic peptides can be utilized to synthetically construct large peptides or polypeptides from shorter peptide fragments. This method consists of a two step chemical reaction (Dawson et al. Synthesis of Proteins by Native Chemical Ligation. Science, 266:776-779 (1994)). The first step is the chemoselective reaction of an unprotected synthetic peptide-α-thioester with another unprotected peptide segment containing an amino-terminal Cys residue to give a thioester-linked intermediate as the initial covalent product. Without a change in the reaction conditions, this intermediate undergoes spontaneous, rapid intramolecular reaction to form a native peptide bond at the ligation site. Application of this native chemical ligation method to the total synthesis of a protein molecule is illustrated by the preparation of human interleukin 8 (IL-8) (Baggiolini M et al. (1992) FEBS Lett. 307:97-101; Clark-Lewis I et al., J. Biol. Chem., 269:16075 (1994); Clark-Lewis I et al., Biochemistry, 30:3128 (1991); Rajarathnam K et al., Biochemistry 33:6623-30 (1994)).

Alternatively, unprotected peptide segments can be chemically linked where the bond formed between the peptide segments as a result of the chemical ligation is an unnatural (non-peptide) bond (Schnolzer, M et al. Science, 256:221 (1992)). This technique has been used to synthesize analogs of protein domains as well as large amounts of relatively pure proteins with fall biological activity (deLisle Milton R C et al., Techniques in Protein Chemistry IV. Academic Press, New York, pp. 257-267 (1992)).

The invention also provides fragments of antibodies that have bioactivity. The polypeptide fragments of the present invention can be recombinant proteins obtained by cloning nucleic acids encoding the polypeptide in an expression system capable of producing the polypeptide fragments thereof, such as an adenovirus or baculovirus expression system. For example, one can determine the active domain of an antibody from a specific hybridoma that can cause a biological effect associated with the interaction of the antibody with FcRH. For example, amino acids found to not contribute to either the activity or the binding specificity or affinity of the antibody can be deleted without a loss in the respective activity.

For example, amino or carboxy-terminal amino acids can be sequentially removed from either the native or the modified non-immunoglobulin molecule or the immunoglobulin molecule and the respective activity assayed in one of many available assays. In another example, a fragment of an antibody can comprise a modified antibody wherein at least one amino acid has been substituted for the naturally occurring amino acid at a specific position, and a portion of either amino terminal or carboxy terminal amino acids, or even an internal region of the antibody, has been replaced with a polypeptide fragment or other moiety, such as biotin, which can facilitate in the purification of the modified antibody. For example, a modified antibody can be fused to a maltose binding protein, through either peptide chemistry of cloning the respective nucleic acids encoding the two polypeptide fragments into an expression vector such that the expression of the coding region results in a hybrid polypeptide. The hybrid polypeptide can be affinity purified by passing it over an amylose affinity column, and the modified antibody receptor can then be separated from the maltose binding region by cleaving the hybrid polypeptide with the specific protease factor Xa. (See, for example, New England Biolabs Product Catalog, 1996, pg. 164.). Similar purification procedures are available for isolating hybrid proteins from eukaryotic cells as well.

The fragments, whether attached to other sequences, can also include insertions, deletions, substitutions, or other selected modifications of particular regions or specific amino acids residues, provided the activity of the fragment is not significantly altered or impaired compared to the nonmodified antibody or antibody fragment. These modifications can provide for some additional property, such as to remove or add amino acids capable of disulfide bonding, to increase its bio-longevity, to alter its secretory characteristics, etc. In any case, the fragment must possess a bioactive property, such as binding activity, regulation of binding at the binding domain, etc. Functional or active regions of the antibody may be identified by mutagenesis of a specific region of the protein, followed by expression and testing of the expressed polypeptide. Such methods are readily apparent to a skilled practitioner in the art and can include site-specific mutagenesis of the nucleic acid encoding the antigen. (Zoller M J et al. Nucl. Acids Res. 10:6487-500 (1982).

As used herein, the phrase “specific binding” or “selective binding” refers to a binding reaction which is determinative of the presence of the FcRH in a heterogeneous population of proteins and other biologics. Thus, under designated conditions, the antibodies or fragments thereof of the present invention bind to a particular FcRH (e.g., human FcRH 1 or any variant thereof), fragment, or variant thereof and do not bind in a significant amount to other proteins (e.g., human FcRH 2, 3, 4, 5, or 6), present in the subject. The absence of binding in the present invention is concisderd to be binding that is less than 1.5 times background (i.e., the level of non-specific binding or slightly above non-specific binding levels),

Selective binding to an antibody under such conditions may require an antibody that is selected for its specificity for a particular protein, variant, or fragment. In one embodiment the purified antibody selectively binds to the FcRH comprising a cytoplasmic region with more than 107 or less than 104 amino acids, a transmembrane region, and an extracellular region. More specifically, the antibody in alternative embodiments selectively binds FcRH1 but not FcRH2-6; selectively binds FcRH2 but not 1 or 3-6; selectively binds FcRH3 but not FcRH1-2 or 4-6; selectively binds FcRH6 but not 1-5. Thus, as one embodiment, the antibody selectively binds a polypeptide comprising the amino acid sequence of SEQ ID NO:1, 21, or 2, or a subset thereof, but not to polypeptides comprising the amino acid of SEQ ID NO:3, 22, 4, 5, 23, 24, 6, 25, 26, 27, 28, or a subset thereof. In another embodiment the purified antibody binds to the FcRH comprising the amino acid sequence of SEQ ID NO:3, 22, or 4, but not to the FcRH comprising the amino acid of SEQ ID NO:1, 21, 2, 5, 23, 24, 6, 25, 26, 27, or 28. In yet another embodiment, the purified antibody that binds to the FcRH comprising the amino acid sequence of SEQ ID NO:5, 23, 24, or 6, but not to the FcRH comprising the amino acid of SEQ ID NO:1, 21, 2, 3, 22, 4, 26, 27, 28. Similarly, the antibodies of the present invention may bind only moFcRH1, but not moFcRH 2 or moFcRH3; may bind only FcRH2 and not FcRH1 or FcRH3, and may bind only FcRH3 and not FcRH1 or FcRH2.

In certain embodiments, the antibody binds the extracellular region of one or more FcRHs and in other embodiments the antibody binds the cytoplasmic region of one or more FcRHs. In other embodiments the antibody may selectively bind one isoform of a FcRH. For example, the antibody may bind a polypeptide having the amino acid sequence of SEQ ID NO:23 but not the SEQ ID NO:24 or vice versa. Furthermore, the antibody can bind to moFcRH1 having the amino acid sequence of SEQ ID NO:70, but not to a moFcRH1 having amino acid sequence of SEQ ID NO:68. The antibody may selectively bind a moFcRH2 with a transmembrane region (e.g., having amino acid sequence of SEQ ID NO:73), but not bind to a moFcRH2 lacking a transmembrane region (e.g., having the amino acid sequence of 77). Optionally the antibody of the invention can selectively bind moFcRH but not human, or vice versa.

A variety of immunoassay formats may be used to select antibodies that selectively bind with a particular protein, variant, or fragment. For example, solid-phase ELISA immunoassays are routinely used to select antibodies selectively immunoreactive with a protein, variant, or fragment thereof. See Harlow and Lane. Antibodies, A Laboratory Manual. Cold Spring Harbor Publications, New York, (1988), for a description of immunoassay formats and conditions that could be used to determine selective binding. The binding affinity of a monoclonal antibody can, for example, be determined by the Scatchard analysis of Munson et al., Anal. Biochem., 107:220 (1980).

The Invention also provides an antibody reagent kit comprising the antibody or fragment thereof of the invention and reagents for detecting binding of the antibody or fragment thereof to a ligand. The kit can further comprise containers containing the antibody or fragment thereof of the invention and containers containing the reagents. Preferably the ligand is a FcRH, variant, or fragment thereof, Particularly, the kit can detect the presence of one or more FcRHs specifically reactive with the antibody or an immunoreactive fragment thereof. The kit can include an antibody bound to a substrate, a secondary antibody reactive with the antigen and a reagent for detecting a reaction of the secondary antibody with the antigen. Such a kit can be an ELISA kit and can comprise the substrate, primary and secondary antibodies when appropriate, and any other necessary reagents such as detectable moieties, enzyme substrates and color reagents as described above, The diagnostic kit can alternatively, be in immunoblot kit generally comprising the components and reagents described herein. Alternatively, the kit could be a radioimmunoassay kit, a Western blot assay kit, an immunohistological assay kit, an immunocytochemical assay kit, a dot blot assay kit, a fluorescence polarization assay kit, a scintillation proximity assay kit, a homogeneous time resolved fluorescence assay kit, or a BIACORE® analysis kit (Pharmacia, Sweden).

As used throughout methods of detectina an PeRil or antigen/antibody complexes, including complexes comprising an FCRH and optionally the antibody of the present invention, can comprise an ELISA (competition or sandwich), a radioimmunoassay, a Western blot assay, an immunohistological assay, an immunocytochemical assay, a dot blot assay, a fluorescence polarization assay (Jolley (1981); Jiskoot et al (1991); Seethala et al. (1998); Bicainuinpaka et al. (1998)), a scintillation proximity assay (Amersham Life Science (1995) Proximity News, Issue 17; Amersham Life Science (1995) Proximity News. Issue 18; Park et al. (1999)), a homogeneous time-resolved fluorescence assay (Park et al. (1999); Stenroos et al. (1988); Morrison, 1988)), or a BIACORE® (Pharmacia, Sweden) analysis (Fägerstam et al. (1992) Chromatography 597:397-410). Preferably, the antigen/antibody complex is detectably tagged either directly or indirectly. Any desired tag can be utilized, such as a fluorescent tag, a radiolabel, a magnetic tag, or an enzymatic reaction product.

Optionally, the antibody or fragment is a humanized antibody or a fully human antibody. For example, the antibodies can also be generated in other species and “humanized” for administration to humans. Alternatively, fully human antibodies can also be made by immunizing a mice or other species capable of making a fully human antibody (e.g., mice genetically modified to produce human antibodies), screening clones that bind FcRH. See, e.g., Lonberg and Huszar (1995) Human antibodies from transgenic mice, Int. Rev. Immunol. 13:65-93, which is incorporated herein by reference in its entirety for methods of producing fully human antibodies. As used herein, the term “humanized” and “fully human” in relation to antibodies, relate to any antibody which is expected to elicit a therapeutically tolerable weak immunogenic response in a human subject.

Humanized forms of non-human (e.g., murine) antibodies are chimeric immunoglobulins, immunoglobulin chains or fragments thereof (such as Fv, Fab, Fab′, F(ab′)₂, or other antigen-binding subsequences of antibodies) which contain minimal sequence derived from non-human immunoglobulin. Humanized antibodies include human immunoglobulins (recipient antibody) in which residues from a complementary determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat or rabbit having the desired specificity, affinity and capacity. In some instances, Fv framework residues of the human immunoglobulin are replaced by corresponding non-human residues. Humanized antibodies may also comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. In general, the humanized antibody will comprise substantially all or at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin consensus sequence. The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region Fc), typically that of a human immunoglobulin (Jones et al., Nature, 321:522-525 (1986); Riechmann et al., Nature, 332:323-327 (1988); and Presta, Curr. Op. Struct. Biol., 2:593-596 (1992)).

Methods for humanizing non-human antibodies are well known in the art. Generally, a humanized antibody has one or more amino acid residues introduced into it from a source that is non-human. These non-human amino acid residues are often referred to as “import” residues, which are typically taken from an “import” variable domain. Humanization can be essentially performed following the method of Winter and co-workers (Jones et at, Nature, 321:522-525 (1986); Riechmann et al., Nature, 332:323-327 (1988); Verhoeyen et al., Science, 239:1534-1536 (1988)), by substituting rodent CDRs or CDR sequences for the corresponding sequences of a human antibody. Accordingly, such “humanized” antibodies are chimeric antibodies (U.S. Pat. No. 4,816,567), wherein substantially less than an intact human variable domain has been substituted by the corresponding sequence from a non-human species. In practice, humanized antibodies are typically human antibodies in which some CDR residues and possibly some FR residues are substituted by residues from analogous sites in rodent antibodies.

The choice of human variable domains, both light and heavy, to be used in making the humanized antibodies is very important in order to reduce antigenicity. According to the “best-fit” method, the sequence of the variable domain of a rodent antibody is screened against the entire library of known human variable domain sequences. The human sequence which is closest to that of the rodent is then accepted as the human framework (FR) for the humanized antibody (Sims et al., J. Immunol., 151:2296 (1993) and Chothia et al., J. Mol. Biol., 196:901 (1987)). Another method uses a particular framework derived from the consensus sequence of all human antibodies of a particular subgroup of light or heavy chains. The same framework may be used for several different humanized antibodies (Carter et al., Proc. Natl. Acad. Sci. USA, 89:4285 (1992); Presta et al., J. Immunol., 151:2623 (1993)).

It is further important that antibodies be humanized with retention of high affinity for the antigen and other favorable biological properties. To achieve this goal, according to a preferred method, humanized antibodies are prepared by a process of analysis of the parental sequences and various conceptual humanized products using three dimensional models of the parental and humanized sequences. Three dimensional immunoglobulin models are commonly available and are familiar to those skilled in the art. Computer programs are available which illustrate and display probable three-dimensional conformational structures of selected candidate immunoglobulin sequences. Inspection of these displays permits analysis of the likely role of the residues in the functioning of the candidate immunoglobulin sequence, i.e., the analysis of residues that influence the ability of the candidate immunoglobulin to bind its antigen. In this way, FR residues can be selected and combined from the consensus and import sequence so that the desired antibody characteristic, such as increased affinity for the target antigen(s), is achieved. In general, the CDR residues are directly and most substantially involved in influencing antigen binding (see, WO 94/04679 published 3 Mar. 1994).

Transgenic animals (e.g., mice) that are capable, upon immunization, of producing a full repertoire of human antibodies in the absence of endogenous immunoglobulin production can be employed. For example, it has been described that the homozygous deletion of the antibody heavy chain joining region (J(H)) gene in chimeric and germ-line mutant mice results in complete inhibition of endogenous antibody production. Transfer of the human germ-line immunoglobulin gene array in such germ-line mutant mice will result in the production of human antibodies upon antigen challenge (see, e.g., Jakobovits et al., Proc. Natl. Acad. Sci. USA, 90:2551-255 (1993); Jakobovits et al., Nature, 362:255-258 (1993); Bruggemann et al., Year in Immuno., 7:33 (1993)). Human antibodies can also be produced in phage display libraries (Hoogenboom et al., J. Mol. Biol., 227:381 (1991); Marks et al., J. Mol. Biol., 222:581 (1991)). The techniques of Cote et al. and Boerner et al. are also available for the preparation of human monoclonal antibodies (Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985); Boerner et al., J. Immunol., 147(l):86-95 (1991)).

In one embodiment, the antibody or fragment thereof is a single chain antibody. In another embodiment, the antibody or fragment is labeled. Optionally the antibody or fragment is conjugated or fused with a toxin or fragment thereof. Examples of the toxin or toxin moiety include diphtheria, ricin, and modifications thereof.

Diagnosis and Treatment

The invention provides uses of the reagents described herein in in vitro and iii vivo methods of diagnosing and treating a malignancy of hematopoietic cell lineage or an autoimmune disease in a subject. The reagents of the present invention are also useful in screening for disease manifestations. Such screening may be useful even before the onset of other clinical symptoms and could be used to screening subjects at risk for disease, so that prophylactic treatment can be started before the manifestation of other signs or symptoms.

By “malignancy” is meant a tumor or neoplasm whose cells possess one or more nuclear or cytoplasmic abnormalities, including, for example, high nuclear to cytoplasmic ratio, prominent nucleolar/nucleoli variations, variations in nuclear size, abnormal mitotic figures, or multinucleation. “Malignancies of hematopoietic cell lineage” include, but are not limited to, myelomas, leukemias, lymphomas (Hodgkin's and non-Hodgkin's forms), T-cell malignancies, B-cell malignancies, and lymphosarcomas or other malignancies described in the REAL classification system or the World Health Organization Classification of Hematologic Malignancies. It should be noted that the absence or presence of specific FcRHs can be diagnostic for a particular malignancy of hematopoietic cell linage or can be diagnostic for a particular form of a malignancy (e.g., a specific form of leukemia).

By “inflammatory and autoimmune diseases” illustratively including systemic lupus erythematosus, Hashimoto's disease, rheumatoid arthritis, graft-versus-host disease, Sjögren's syndrome, pernicious anemia, Addison disease, scleroderma, Goodpasture's syndrome, Crohn's disease, autoimmune hemolytic anemia, sterility, myasthenia gravis, multiple sclerosis, Basedow's disease, thrombopenia purpura, insulin-dependent diabetes mellitus, allergy; asthma, atopic disease; arteriosclerosis; myocarditis; cardiomyopathy; glomerular nephritis; hypoplastic anemia; rejection after organ transplantation and numerous malignancies of lung, prostate, liver, ovary, colon, cervix, lymphatic and breast tissues.

Specifically, the diagnostic methods comprise the steps of contacting a biological sample of the subject with an antibody or nucleic acid of the invention under conditions that allow the antibody to bind to cells of hematopoietic cell lineage or allow the nucleic acid to hybridize, preferably under stringent conditions, with nucleic acids of the biological sample; and detecting the amount or pattern of binding. Changes in the amount or pattern of binding as compared to binding in a control sample indicate a malignancy or an inflammatory or autoimmune disease.

In various embodiments, the antibody used in the diagnostic method can selectively bind with an FcRH having the amino acid sequence of SEQ ID NO:1, 21, 2, 3, 22, 4, 5, 24, or 6.

The detecting step of the diagnostic method can be selected from methods routine in the art. For example, the detection step can be performed in vivo using a noninvasive medical technique such as radiography, fluoroscopy, sonography, imaging techniques such as magnetic resonance imaging, and the like. In vitro detection methods can be used to detect bound antibody or fragment thereof in an ELISA, RIA, immunohistochemically, FACS, IHC, FISH, or similar assays.

As used throughout, “biological sample” refers to a sample from any organism. The sample can be, but is not limited to, peripheral blood, plasma, urine, saliva, gastric secretion, feces, bone marrow specimens, primary tumors, embedded tissue sections, frozen tissue sections, cell preparations, cytological preparations, exfoliate samples (e.g., sputum), fine needle aspirations, amnion cells, fresh tissue, dry tissue, and cultured cells or tissue. It is further contemplated that the biological sample of this invention can also be whole cells or cell organelles (e.g., nuclei). The sample can be unfixed or fixed according to standard protocols widely available in the art and can also be embedded in a suitable medium for preparation of the sample. For example, the sample can be embedded in paraffin or other suitable medium (e.g., epoxy or acrylamide) to facilitate preparation of the biological specimen for the detection methods of this invention.

The invention also provides a method of treating a malignancy of hematopoietic cell lineage or an inflammatory or autoimmune disease in a subject, comprising contacting the subject's malignant cells or inflammatory cells with a therapeutically effective amount of a reagent (e.g., an antibody or nucleic acid) or a therapeutic composition of a reagent of the invention. The contacting step can occur by administration of the reagent or composition using any number of means available in the art. Typically, the reagent or composition is administered to the subject transdermally (e.g., by a transdermal patch or a topically applied cream, ointment, or the like), orally, subcutaneously, intrapulmonaryily, transmucosally, intraperitoneally, intrauterinely, sublingually, intrathecally, intramuscularly, intraarticularly, etc. using conventional methods. In addition, the reagent or composition can be administered via injectable depot routes such as by using 1-, 3-, or 6-month depot injectable or biodegrable materials and methods.

Regardless of the route of administration, the amount of the reagent administered or the schedule for administration will vary among individuals based on age, size, weight, condition to be treated, mode of administration, and the severity of the condition. One skilled in the art will realize that dosages are best optimized by the practicing physician and methods for determining dosage are described, for example in Remington's Pharmaceutical Science, latest edition. Guidance in selecting appropriate doses for antibodies is found in the literature on therapeutic uses of antibodies, e.g., Handbook of Monoclonal Antibodies, Ferrone et al., eds., Noges Publications, Park Ridge, N.J., (1985) ch. 22 and pp. 303-357; Smith et al., Antibodies in Human Diagnosis and Therapy, Haber et al., eds., Raven Press, New York (1977) pp. 365-389. A typical dose of the antibody used alone might range from about 1 μg/kg to up to 100 mg/kg of body weight or more per day, and preferably 1 μg/kg to up to 1 mg/kg, depending on the factors mentioned above. An intravenous injection of the antibody or fragment thereof, for example, could be 10 ng-1 g of antibody or fragment thereof, and preferably 10 ng-1 mg depending on the factors mentioned above. For local injection, a typical quantity of antibody ranges from 1 pg to 1 mg. Preferably, the local injection would be at an antibody concentration of 1-100 μg/ml, and preferably 1-20 μg/ml.

The nucleic acids of the invention can delivered to cells in a variety of ways. For example, if the nucleic acid of this invention is delivered to the cells of a subject in an adenovirus vector, the dosage for administration of adenovirus to humans can range from about 10⁷ to 10⁹ plaque forming units (pfu) per injection, but can be as high as 10¹² pfu per injection. Ideally, a subject will receive a single injection. If additional injections are necessary, they can be repeated at six month intervals for an indefinite period and/or until the efficacy of the treatment has been established. As set forth herein, the efficacy of treatment can be determined by evaluating the clinical parameters.

The exact amount of the nucleic acid or vector required will vary as described above. Thus, it is not possible to specify an exact amount for every nucleic acid or vector. An appropriate amount can be determined by one of ordinary skill in the art using only routine experimentation given the teachings herein.

The invention further provides a therapeutic composition of the reagent of the invention. Such a composition typically contains from about 0.1 to 90% by weight (such as 1 to 20% or 1 to 10%) of a therapeutic agent of the invention in a pharmaceutically acceptable carrier. Solid formulations of the compositions for oral administration may contain suitable carries or excipients, such as corn starch, gelatin, lactose, acacia, sucrose, microcrystalline cellulose, kaolin, mannitol, dicalcium phosphate, calcium carbonate, sodium chloride, or alginic acid. Disintegrators that can be used include, without limtation, microcrystalline cellulose, corn starch, sodium starch, glycolate, and alginic acid. Table binders that may be used include acacia, methylcellulose, sodium carboxymethlcellulose, polyvinylpyrrolindone (Povidone), hydroxypropyl methylcellulose, sucrose, starch, and ethylcellulose. Lubricants that may be used include magnesium stearates, stearic acid, silicone fluid, talc, waxes, oils, and colloidal silica.

Liquid formulations for oral administration prepared in water or other aqueous vehicles may contain various suspending agents such as methylcellulose, alginates, tragacanth, pectin, kelgin, carrageenan, acacia, polyvinylpyrrolidone, and polyvinyl alcohol. The liquid formulations may also include solutions, emulsions, syrups and elixirs containing, together with the active compound(s), wetting agents, sweeteners, and coloring and flavoring agents. Various liquid and powder formulations can be prepared by conventional methods for inhalation into the lungs of the mammal to be treated.

Injectable formulations of the compositions may contain various carriers such as vegetable oils, dimethylacetamide, dimethylformamide, ethyl lactate, ethyl carbonate, isopropyl myristate, ethanol, polyols (glycerol, propylene glycol, liquid polyethylene glycol, and the like). For intravenous injections, water soluble version of the compounds may be administered by the drip method, whereby a pharmaceutical formulation containing the antifungal agent and a physiologically acceptable excipient is infused. Physiologically acceptable excipients may include, for example, 5% dextrose, 0.9% saline, Ringer's solution or other suitable excipients. Intramuscular preparations, e.g., a sterile formulation of a suitable soluble salt form of the compounds, can be dissolved and administered in a pharmaceutical excipient such as water-for-injection, 0.9% saline, or 5% glucose solution. A suitable insoluble form of the compound may be prepared and administered as a suspension in an aqueous base or a pharmaceutically acceptable oil base, such as an ester of a long chain fatty acid (e.g., ethy, oleate).

A topical semi-solid ointment formulation typically contains a concentration of the active ingredient from about 1 to 20%, e.g., 5 to 10%, in a carrier such as a pharmaceutical cream base. Various formulations for topical use include drops, tinctures, lotions, creams, solutions, and ointments containing the active ingredient and various supports and vehicles. The optimal percentage of the therapeutic agent in each pharmaceutical formulation varies according to the formulation itself and the therapeutic effect desired in the specific pathologies and correlated therapeutic regimens.

The effectiveness of the method of treatment can be assessed by monitoring the patient for known signs or symptoms of the conditions being treated. For example, in the treatment of a malignancy of hematopoietic cell lineage, the reduction or stabilization of the number of abnormally proliferative cells would indicate successful treatment. In the treatment of arthritis, for example, a reduction in the amount of joint inflammation would indicate successful treatment. Thus, by “therapeutically effective” is meant an amount that provides the desired treatment effect.

The invention further provides a method of modulating a humoral immune response in a subject, comprising administering to the subject an isolated FcRH, an antibody, or nucleic acid of the invention. By “modulation” is meant either up-regulating or down-regulating. Thus, in the case of an allergic response, one skilled in the art would choose to down-regulate the humoral immune response. In the case of exposure of a subject to an infectious agent (e.g., a viral or bacterial agent), one skilled in the art would choose to upregulate the humoral antibody response.

Experimental

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C. or is at ambient temperature, and pressure is at or near atmospheric.

EXAMPLE 1 Identification of FcRH1, FcRH2, and FcRH3

In order to isolation of FcRH cDNA Clones, rapid amplification of cDNA ends (RACE)-PCR was performed by using a Marathon-Ready™ human lymph node cDNA library (CLONTECH, Mountain View, Ca), Gene-specific primers were as follows: FcRH3, forward 5′-TGAGTCTCAGGGTCACAGTTCCG -3′ (SEQ ID NO41) and reverse 5′-GCTCTTGAACTTGGATATTTAGGGGT3′ SEQ ID NO: 42); FcRH2, forward 5′-CCAGTGTATGTCAATGTGGGCTCTG3′ (SEQ ID NO: 43) and reverse 5′-CGTTGAAAGAGCTCTTGGACTTTTATC3′ (SEQ ID NO:44); and FeRH 1, forward 5′-GCCTCAAAAGAAAAATAGCAAGACGTT3′ (SEQ ID NO: 45) and reverse 5′-AAGCTCACATCAGCGACAGGGAC-3′ (SEQ ID NO: 46). RACE products were subjected to a second round of nested PCR and visualized by agarose gel electrophoresis and ethidium bromide staining.

Primers used in end-to-end amplification to generate full-length cDNAs were as follows: FcRH3, forward 5′-TCTTGGAGATAAGTCGGGCTTT-3′ (SEQ ID NO:47) and reverse 5′-ATCCTGCAGCCCAGCCTCGTAGGAG-3′ (SEQ ID NO:48); FcRH2, forward 5′-GGTCCTCATGCTGCTGTGGTCATT-3′ (SEQ ID NO:49)and reverse 5′-GCTGTTGATCTTCCCTTCTGATTC-3′ (SEQ ID NO:50); and FcRH1, forward 5′-ATGCTGCCGAGGCTGTTGCTGTTG3′ (SEQ ID NO:51) and reverse 5′-CATAGCATCTTCATAGTCCACATC-3′ (SEQ ID NO:52). Each amplification reaction underwent initial denaturation of 94° C. for 30 s followed by 30 cycles of denaturation at 94° C. for 5 s and annealing at 68° C. for 4 min, and final extension at 72° C. for 6 min.

PCR. products were ligated into the pCR2.1 TOPO T/A vector (Invitrogen, Carlsbad, CA). Inserts were DNA-sequenced on both strands by the dideoxy chain termination method using Thermo Sequenase (Amersham Pharmacia, Piscataway, NJ) and an automated sequencer (Li-Cor, Lincoln, Nebr.). Nucleotide and amino acid sequence alignment was analyzed with a DNASTAR™ (DNAStar, Madison, Wis.) software package, and homology searches were performed by using BLASE (Altschul, S. F. et al. (1990) J. Mol. Biol. 215,403-410).

RNA blot analysis was subsequently performed. Northern blots (CLONTECH) were hybridized with 32P-dCTP-labeled probes: a 528-bp EcoRI fragment corresponding to the 5′ untranslated (UT)-EC1 regions of the FcRH3 cDNA, a 200-bp PCR product corresponding to a portion of the 3′ UT region of the FcRH2 cDNA, and a 257-bp PCR product corresponding to a portion of the 3′ UT region of the FcRH1 cDNA. Membranes were hybridized for 1 h at 65° C., washed, and exposed to x-ray film (Kubagawa, H. et al. (1997) Proc. Natl. Acad. Sci. USA 94, 5261-5266).

Reverse transcription (RT)-PCR was performed Human tonsillar cells, obtained with Institutional Review Board approval, were separated into CD19+and CD19 subpopulations by magnetic cell sorting (Miltenyi Biotec, Auburn, Calif.). Viable CD19+ cells were stained with FITC-labeled anti-CD38 (Immunotech, Westhrook, Me.) and phycoerytbrin-labeled anti-IgD mAbs (Southern Biotechnology Associates, Birmingham, AL) before sorting cells with a FACSTARPLUS™ instrument (Becton Dickinson, Franklin Lakes, NJ) into TRIZOL® reagent (Life Technologies, Grand Island, N.Y. ) for RNA isolation. Total cellular RNA was primed with random hexamers and oligo(dT) primers and reverse-transcribed with SUPERSCRIPT™ II Invitrogen, Carlsbad, CA) into single stranded cDNA. RT-PCR was performed by using RNA from tonsillar B cells and cell lines, with GIBCO/BRL Taq polymerase (Life Technologies). The following gene-specific primer pairs were used in the RT-PCR analysis of FcRH1-5 expresion in cell lines and tonsillar B cell subpopulations: FcRH1 forward, 5′-CTC AACTTC ACA GTG CCT ACT GGG-3′ (SEQ ID NO:53) and reverse, 5′-TCC TGC AGA GTC ACT AACCTT GAG-3′ (SEQ ID NO:54): FcRH-2 forward, 5′-CCA GTG TAT GTC AAT GTG GGC TCT G (SEQ ID NO:55) and reverse, 5′-CAT TCT TCC CTC AAA TCT TTA CAC-3′ (SEQ ID NO:56); FcRH3 forward, 5′-CAG CAC GTG GAT TCG AGT CDC-3′ (SEQ ID NO:57) and reverse, 5′-CAG ATC TGG GAA TAA ATC GGG TTG3′ (SEQ ID NO:58)fcRH4 forward, 5′-TCT TCA GAG ATC GGG AGG TGA-3′ (SEQ ID NO:59) and reverse, 5′-TTT TGG GGT GTA CAT CAA CAT ACA AG-3′ (SEQ ID NO:60); and FcRH forward, 5′-TGT TGC CCT GTT TCT TCC ATT ACA-3′ (SEQ ID NO:61) and reverse, 5′CAG ACT TGG CCG ACC TAC GC-3′ (SEQ ID NO:62) Each amplification reaction underwent initial denaturation at 94. degree, for 5 min followed by 35 cycles of denaturation at 94. degree for 30 s, annealing at 60 degree. for 30 s, extension at 72.degree. for 1 min, and final extension at 72. degree. for 7 min. Amplified products were visualized in 1% agarose gels containing ethidium bromide and documented with the BIO-RAD FLUOR-S™ IMAGER (Bio-Rad Laboratories, Hercules, CA).

The following human cell lines were used: REH and Nalm 16 pro-B cell lines (Korsmeyer, S. J. et al. (1983) J. Clin. Invest. 71, 301-313); 697, 207, and OB5 pre-B cell lines (Findley, H. W. et al. (1982) Blood 60, 1305-1309; Martin, D. et al. (1991) J. Exp. Med. 173, 639-645); Ramos, Daudi, and Raji B cell lines (Pulvertaft, R. J. V. (1964) Lancet 1, 238-240; Klein, E. et al. (1968) Cancer Res. 28, 1300-1310; Klein, G. et al. (1975) Intervirology 5, 319-33431-33); THP-1 and U937 monocytoid cell lines, HL-60 promyelocytic and KG-1 myelocytic cell lines, Jurkat T cell line and the K562 erythroid cell line (American Type Culture Collection).

A consensus sequence was generated that corresponds to the GenBank-derived amino terminal sequences of the second Ig-like domains of FcR (FcγRI and FcγRII/III) and the third Ig-like domain of the polymeric Ig receptor:GEPIXLRCHSWKDKXLXKVTYXQNGKAXKFFH (SEQ ID NO:63). A search of the National Center for Biotechnology Information protein database with this sequence identified two overlapping human genomic bacterial artificial chromosome (BAC) clones, AL135929 and AL356276, which are located at 1q21.2-22. The second clone contained three putative Ig superfamily genes encoding complementary amino acid sequences that were designated FcRH1, FcRH2, and FcRH3. See FIG. 1. The predicted amino acid sequences of these gene segments shared 23-57% identity with each other and 14-28% identity with human FcγRI (CD64). Further analysis of the FcRH locus led to the identification of two additional genes (FcRH4, and FcRH5) and one pseudogene (FcRH4ψ), immediately centromeric of FcRH1-3, two of which have recently been described as IRTA1 (FcRH4) and IRTA2 (FcRH5) (Hatzivassiliou, G. et al. (2001) Immunity 14, 277-289).

To determine whether these genes are expressed by lymphocytes, the predicted amino acid sequences of their protein products were used to search the Lymphochip expressed sequence tag database with the TBLASTN algorithm (Alizadeh, A. A. et al. (2000) Nature (London) 403, 503-511). Two expressed sequence tags (AA505046 and AA282433) were identified that share complete identity over 23 amino acids in their translated ORFs with the N terminus of FcRH1. Lymphochip microarray data analysis indicated that these expressed sequence tags are expressed at relatively high levels in peripheral lymphoid tissues, including the lymph nodes, tonsils, resting peripheral B cells, and normal germinal center (GC) B cells. Among the different lymphoid malignancies, their expression proved to be highest in chronic lymphocytic leukemias, follicular lymphomas, and some diffuse large cell lymphomas of B lineage.

FcRH1, FcRH2, and FcRH3 cDNAs were isolated by RACE-PCR from a human lymph node cDNA library in both 5′ and 3′ directions. Full-length cDNAs of the coding regions for FcRH1, FcRH2, and FcRH3 were obtained by end-to-end PCR using unique primers generated from the cDNA sequences delineated for the 5′ UT and 3′UT regions. Southern blot analysis of human genomic DNA digested with BamHI, EcoRI, or HindIII using cDNA probes specific for the 3′ UT regions of each cDNA revealed either one or two hybridizing fragments, suggesting that FcRH1, FcRH2, and FcRH3 are encoded by single genes. Analysis of full-length cDNA sequences indicated that FcRH1, FcRH2, and FcRH3 have ORFs of 1,287 bp, 1,524 bp, and 2,202 bp, respectively, and encode type I transmembrane proteins of 429 aa, 508 aa, and 734 aa, respectively. Based on predicted consensus signal peptide cleavage sites (Von Heijne, G. (1986) Nucleic Acid Res. 14, 4683-4690; Nielsen, H. (1997) Protein Eng. 10, 1-6), the relative core peptide molecular masses were estimated as 45,158 for FcRH1, 53,407 for FcRH2, and 78,849 for FcRH3. These type I transmembrane proteins possess 3-6 extracellular C2 (Williams, A. F. & Barclay, A. N. (1988) Annu. Rev. Immunol. 6, 381-405; Bork, P. et al. (1994) J. Mol. Biol. 242, 309-320; Vaughn, D. E. & Bjorkman, P. J. (1996) Neuron 16, 261-273) type Ig-like domains with 3-7 potential N-linked glycosylation sites, uncharged transmembrane segments, and relatively long cytoplasmic tails containing consensus motifs for ITIMs and/or ITAMs. See FIG. 2A.

Multiple alignment analysis of the translated cDNAs, using FcRH3 as the index sequence of comparison, indicates that FcRH1, FcRH2, and FcRH3 have highly conserved hydrophobic signal peptides and corresponding Ig-like extracellular domains (FIG. 2B). Their hydrophobic transmembrane (uncharged with the exception of FcRH1 which includes an acidic domain) domains (Sonnhammer, E. L. L. et al. (1998) in A Hidden Markov Model for Predicting Transmembrane Helices in Protein Sequences, eds. Glasgow, J., Littlejohn, T., Major, F., Lathrop, R., Sankoff, D. & Sensen, C. (Am. Assoc. for Artificial Intelligence, Menlo Park, Calif.), pp. 175-182) are also well conserved, but their cytoplasmic domains are not. FcRH1 has a long cytoplasmic tail containing three potential ITAMs, the first and third of which fit the consensus sequence (E/D)-X-X-Y-X-X-(L/I)-X₆₋₈-Y-X-X-(L/I) (SEQ ID NO:64, with six amino acid between the consensus sequences; SEQ ID NO:65, with seven amino acid residues between the consensus sequences; and SEQ ID NO:66, with eight amino acid residues between the consensus sequences), whereas, the second has only one tyrosine residue. The shorter cytoplasmic domain of FcRH2 contains one potential ITAM and two ITIM consensus sequences (I/V/L/S)-X-Y-X-X-(L/V) (SEQ ID NO:67) separated by 22 amino acids. FcRH3 has the longest cytoplasmic tail. It contains one potential ITAM, one ITIM, and another potential ITAM that also has a single tyrosine residue.

An RNA blot analysis with gene-specific probes was performed on 16 human tissues, including six primary or secondary lymphoid tissues. RNA blots were analyzed with discriminating α³²P-dCTP-labeled probes generated from the respective FcRH cDNAs. The following probes were used: (Top) a PCR-generated, 257-bp probe specific to the 3′ UT region of FcRH1; (Middle) a PCR-generated, 290-bp probe corresponding to the 3′ UT region of FcRH2; and (Bottom) a 528-bp EcoRI-digested fragment of the 5′ end of the FcRH3 cDNA corresponding to its 5′ UT region, S1, S2, and EC1 domains. The relative mRNA abundance was indicated by β-actin probe. All three FcRH gene probes hybridized with transcripts in the secondary lymphoid organs, spleen and lymph node. An FcRH1-specific probe hybridized with spleen and lymph node transcripts of about 3.5 kb and about 6.0 kb. Additional hybridization bands of about 0.7 kb and about 1.5 kb were observed for heart, skeletal muscle, kidney, liver, and, in less abundance, placental tissue. Larger transcripts also were seen in skeletal muscle (about 6.0 kb) and in kidney and placenta (about 4.4 kb). An FcRH2-specific probe hybridized to about 3.0-kb, about 4.4-kb, and about 5.5-kb transcripts most abundantly in spleen and lymph node. A transcript of approximately 2.4-kb was notable in the kidney. An FcRH3 probe hybridized with about 3.5-kb, about 5.5-kb, and about 7.0-kb transcripts chiefly in spleen and lymph node. These also were seen, albeit in lesser abundance, in peripheral blood lymphocytes, thymus, and bone marrow samples. Additionally, a unique transcript of about 1.35 kb was evident in skeletal muscle. These results indicated expression of FcRH1, FcRH2, and FcRH3 in peripheral lymphoid organs, whereas tissue specific differences in alternative splicing or polyadenylation were suggested by the differential expression of transcripts with variable size in nonlymphoid tissues. RTPCR analysis to date of non-lymphoid tissue skeletal muscle, however, does not reveal transcripts despite the Northern analysis results.

When FcRH expression was examined by RT-PCR analysis of cell lines representing different hematopoietic lineages, FcRH1, FcRH2, and FcRH3 expression was found in every mature B cell line tested (Table 2). FcRH2 and FcRH3 expression was limited to the mature B cell lines and not seen in the other types of cells examined. In contrast, FcRH1 expression was seen in pro-B, T, and myeloid cell lines, although not in an erythroid cell line.

TABLE 2 Expression of FcRH transcripts in human B cell lines Cell Type Cell line FcRH1 FcRH2 FcRH3 Pro-B REH + − − Nalm 16 + − − Pre-B 697 − − − 207 − − − OB5 − − − B Ramos + + + Daudi + + + Raji + + + T Jurkat + − − Monocytic THP-1 + − − Myelomonocytic U937 + − − Promyelocytic HL-60 + − − Myelocytic KG-1 + − − Erythroid K562 − − − FcRH1, FcRH2, and FcRH3 expression in cell lines was determined by RT-PCR.

RT-PCR analysis of sorted populations of peripheral blood cells indicated that FcRH1, FcRH2, FcRH3, and FcRH5 are expressed at relatively high levels in CD19+ B cells, whereas FcRH4 was expressed at only trace levels. FcRH3 expression was observed in CD3+ T cells whereas transcripts of FcRH1 were barely detectable. FcRH1 expression also was observed in circulating granulocytes.

To refine the analysis of FcRH expression in secondary lymphoid tissues, tonsillar lymphocyte subpopulations were isolated. The five discrete subpopulations of B lineage cells, which can be distinguished by their differential expression of cell surface IgD and CD38, represent different stages in B cell differentiation: follicular mantle (IgD+CD38), pre-GC (IgD+CD38+), GC (IgDCD38+), memory (IgDCD38), and mature plasma cells (CD38²+) (Pascual, V. (1994) J. Exp. Med. 180: 329-339). RT-PCR analysis of FcRH1-5 expression in tonsillar B cell subpopulations was performed. Viable cells were magnetically sorted into CD19- non-B cells and CD19+ B cells. The latter were stained with anti-IgD and anti-CD38 mAbs, and the five subpopulations indicated (CD38−IgD−, CD38−IgD+, CD38+IgD+, CD38+IgD−, and CD38²+) were sorted by flow cytometry. RT-PCR analysis of FcRH transcripts in non-B cells and the B cell subpopulations was also performed. After cDNA preparation, PCR amplification was performed on the equivalent template of approximately 10 k cells. Glyceraldehyde-3-phosphate dehydrogenase (GADPH) was amplified as a positive control.

RT-PCR analysis indicated little or no expression of FcRH transcripts in the non-B lineage CD19− cells, most of which are T cells. However, CD19+ subpopulations displayed coordinate expression of FcRH1, FcRH2, and FcRH3 transcripts in follicular mantle, naïve, GC, and memory B cell subpopulations, but yielded no evidence of FcRH transcripts in pre-GC B cells or plasma cells. In contrast, FcRH4 transcripts were restricted to the follicular mantle and memory B cells, whereas FcRH5 expression extended to mature plasma cells.

The relationship between the five FcRHs was examined by comparing their full-length, extracellular, and individual Ig-like domain amino acid sequences. This analysis, which included a recently identified mouse FcRH ortholog (moFcRH) and members of the FcR family, used the CLUSTAL method algorithm (Higgins, D. G. & Sharp, P. M. (1989) Comput. Appl. Biosci. 5, 151-153). Comparison of the full-length sequences of other FcRH family members with FcRH3 indicated 40-47% identity. By comparison, the degree of FcRH3 homology with the moFcRH was found to be 35% and 21-24% with FcR members residing on chromosome 1, FcγRI, FcγRII, FcγRIII, and FcεRI. A lower level of amino acid identity (14%) was observed for the chromosome 19 LRC member, FcαR. A slightly higher degree of extracellular homology was evident. Pairwise analysis of the individual Ig-like subunits indicated conservation in membrane-distal to membrane-proximal ordering of extracellular domain composition among family members. Although similar Ig domain subunits were shared among family members, the individual receptors were found to be composed of unique domain combinations. The extracellular domain configuration of the moFcRH most closely resembled that of FcRH2, with which it has 46% identity. The extended pairwise comparison of the FcRH family with known FcRs suggested the conservation of these Ig-like domains to some degree throughout the greater family. The resemblance is particularly evident in the FcRH3 membrane-distal domains that correspond to the three FcγRI domains and the two domains of FcγRII, FcγRIII, and the FcR γ-chain. This analysis suggests the ancestral occurrence of differential duplication and diversification of the individual Ig-like subunits in the respective FcRH family members. The data also indicate that the FcRHs are more similar to their FcR neighbors on chromosome 1 than to their FcR relative on chromosome 19.

The genomic sequence analysis of relevant chromosome 1q21 BAC clones indicated that the entire FcRH locus spans 300 kb. The FcRH genes lie in the same transcriptional orientation toward the centomere. Exon-intron boundaries were characterized by sequence comparison of their respective cDNA clones and the AG/GT rule. The FcRH1 gene consists of 11 exons and 10 introns spanning about 28 kb. The first exon, 5′ UT/S1, encodes the 5′ UT region, the ATG translation initiation codon, and the first half of a split signal peptide. S2, the second exon, is separated from 5′ UT/S1 by a long intron of 12.9 kb and, like the neighboring FcRs, is 21 bp in length (van de Winkel, J. G. & Capel, P. J. (1993) Immunol. Today 14, 215-221; Kulczycki, A., Jr. et al. (1990) Proc. Natl. Acad. Sci. USA 87, 2856-2860; Pang, J. et al. (1994) J. Immunol. 151, 6166-6174.). The extracellular region is encoded by three closely clustered exons, EC1-EC3, that code for the three Ig-like domains. The membrane-proximal, transmembrane, and the proximal portion of the cytoplasmic domain are encoded by a single sixth exon, TM. The cytoplasmic tail is encoded by five exons, CY1-CY5, and the CY5 also encodes the beginning of the 3′ UT region.

FcRH2 contains 12 exons and 11 introns that span 30 kb. It also contains two exons that encode a split signal peptide, the first of which, 5′UT/S1, includes the 5′ UT region, the ATG translation initiation codon, and first half of the signal peptide. The second exon, S2, is 21 bp in length. Exons 3-6 encode the four extracellular domains, EC1-EC4. The seventh exon encodes the membrane-proximal, transmembrane, and the proximal portion of the cytoplasmic domain. The FcRH2 cytoplasmic tail is encoded by five exons, CY1-CY5, the last exon of which includes the termination of the ORF and beginning of the 3′ UT region.

The FcRH3 gene consists of 16 exons and 15 introns that span about 24 kb. Unlike FcRH1 and FcRH2, its 5′ UT region is encoded by two exons, 5′ UT1 and a second, 5′UT2/S1, that also encodes the ATG translation initiation codon and the beginning of the split signal peptide. The third exon, S2, is also 21 bp in length. Extracellular domains encoded by six exons, EC1-EC6, are followed by exon 10 that encodes the membrane-proximal, transmembrane, and the proximal portion of the cytoplasmic domain. The cytoplasmic tail is encoded by five exons, CY1-CY5; the last contains the beginning of the 3′ UT region.

EXAMPLE 2 Identification of HuFcRH6

FcRH6 is located in the midst of the classical FcRs at 1q21-23. Its genomic structure indicates, like the classical FcRs and FcRH1-5, a split hydrophobic signal peptide encoded by two exons the second of which is 21 bp.

FcRH6 was characterized using the methods described in Example 1. A composite analysis of Ig-like domains for relatedness with the other huFcRHs was performed. See Figure xxx. Sequence analysis of huFcRH6 indicates its type I transmembrane form contains a consensus motif for a single ITAM, or a single or two ITIM's.

Initial RT-PCR analysis of huFcRH6 in human tissues and cell lines (as described in Example 1) reveals transcript expression in normal tonsil and lymph nodes. In cell lines, expression of huFcRH6 was identified in myeloid cell lines THP-1 (monocytic), U937 (myelomonocytic), and KG-1 (myelocytic). Limited expression if any was identified in the 207 pre-B cell line and the Daudi B cell line.

EXAMPLE 3 Generation of Transfectants and Antibodies

Recombinant constructs for transfection and stable expression of huFcRH1-5 have been generated. The constructs have been ligated into a CMV driven mammalian expression vector with and without green fluorescent protein (GFP) fusion at the carboxyl terminus. Surface expression of huFcRH1 and huFcRH3 was detected for both GFP and non-GFP forms by staining with antibody supernatant. The antibody supernatant was derived from hybridomas generated by mice immunized with recombinant extracellular protein of the respective FcRH. The constructs for huFcRH2, 4, and 5 have been detected by green fluorescence as well as surface expression for FcRH4.

Monoclonal antibodies have been generated, including, for example, an antibody that binds FcRH1. The preliminary analysis of FACS staining for FcRH1 expression with monoclonal antibody 1-5A3 labeled with a FITC conjugate (mouse anti human FcRH1) in peripheral blood from normal volunteers indicates virtually all CD19+ B cells have huFcRH1 expression, as do CD14+ monocytes and CD13+ granulocytes. CD3+ T cells have limited to no expression of FcRH1. Staining of B-CLL samples from two different patient peripheral blood samples indicates that virtually all CD5+/CD19+ B-CLL cells are positive for the FcRH11-5A3 antigen. By western blot analysis of recombinant protein for FcRH1-5 extracellular regions 1-5A3 appears specific for FcRH1. 1-5A3 also stains B cell lines Daudi and Raji.

EXAMPLE 4 Identification of MoFcRH1-3

A family of three mouse Fc Receptor Homologs (MoFCRHs) were identified and cloned. Amino acid sequences from the membrane proximal Ig like domains of huFcRH1-5 were used to identify putative mouse FcRH orthologs in the NCBI or Celera genomic, EST, and protein databases using the protein BLAST (BLASTP) and the translated nucleotide BLAST (TBLASTN) algorithms, respectively. The location of moFcR family is split between chromosomes 1 and 3 in regions syntenic with human chromosome 1q21-23. See FIG. 4. The mo FcRH are located on mouse 13. Approximate position were determined from Genbank, Celera, and Mouse Genome informatics databases, Contings of ESTs were generated to determine the putative cDNA sequences.

Genomic organization was determined by comparing cDNA clones generated from RACE PCR with GenBank and Celera genomic sequences, DNASTAR™ software DNAStar, MADISON, WI.) was used for analysis of exon-intron boundaries which were characterized by sequence comparison and the AG/GT rule. All three genes contain a split signal sequence with a 21 bp S2 exon (exon 2) which is found in all FcR and huFcRH genes on human chrumosone 1.

A comparison of tyrosine based motifs in FcRH cytoplasmic tails indicated homology with the huFcRH family. See FIG. 5. An analysis of sequence homology conservation is further shown in FIGS. 6 and 7.

Expression of the moFcRHs in tissue and cell lines was also characterized as described in Example 1. Briefly, RT-PCR was performed on mouse tissues and cell lines with gene specific primers. Viable tissue was placed in TRIZOL® reagent (Molecular Research Center Cinncinnati, OH) for RNA extraction. After cDNA preparation PCT amplification was performed on equivalent template amounts. Actin was amplified as a positive control. McFcRH3 appears to have preferential expression in cells of B lineage. The results are shown in Tables 3-4.

TABLE 3 Tissue Distribution of moFcRH Expression TISSUE MoFcRH1 MoFcRH2 MoFcRH3 Bone Marrow + + + Thymus + + + Spleen + + + Lymph Node + + + Peyer's Patches + + + Peripheral Blood + + + Brain + − − Liver + + − Heart + − − Muscle + − − Kidney + − − Lung + + − Intestine + + + Testes + − −

TABLE 4 Expression of moFcRH transcripts in cell lines Cell Type Cell line FcRH1 FcRH2 FcRH3 Pro-B SCID7 + +/− + Raw8.1 + + − Pre-B 70Z/3 + + + BC76 − + + 18-81 + + + Imm. B WEHI-231 + + + WEHI-279 + + + B A20 + + + X16C8.5 + + + T EL4 + +/− −/+ NKT NKT + +/− − NKT 2C12 + +/− − Myeloid WEHI-3 + − − Lymphoid YAC-1 + + − Fibroblast 3T3 + +/− − Expression in cell lines was determined by RT-PCR.

The mouse FcReceptor Homologs include secreted or type I transmembrane isolfrms that have unique cytoplasmic tails with potential activation and inhibition motifs. Their chromosomal location, Ig domain homology, and genomic organization indicate the mouse FcReceptor Homologs are orthologs of the huFcRH that have evolved a significant level of diversity. moFcRH1, moFcRH2, and moFcRH3 are predicted to encode secreted or type I transmembrane proteins based on their amino acid sequences. moFcRH1 has two secreted isoforms both of which have extracellular (EC) regions of four Ig-like domains with five potential sites for N-linked glycosylation. One isoform is a fusion protein with a type B scavenger receptor domain containing 8 cysteines. moFcRH2 has secreted and type I isoforms containing two Ig-like domains with five N-linked glycosylation sites. The type I isoform has an uncharged transmembrane region which the secreted isoform lacks. Both isoforms contain the cytoplasmic portion which is long in the transmembrane form and contains five tyrosines including a consensus sequence for one potential immunoreceptor tyrosine-based activating motif. moFcRH3 contains five Ig-like domains with six potential sites of N-linked glycosylation. Its transmembrane domain is also uncharged and the cytoplasmic region contains one potential ITAM and one potential immunoreceptor tyrosine-based inhibitory motif. The amino acid (aa) length of individual regions and full length (FL) isoforms, as well as approximate molecular weight (MW) in Daltons (Da), is indicated in the structural diagram of FIG. 8.

Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

1. An isolated FcRH6 comprising the amino acid sequence of SEQ ID NO:28. 